This file was automatically generated from entries from the ISI (Institute for Scientific Information) databases of scientific and other academic documents, using isi2bibtex version 0.4, a perl script which converts ISI or BIDS format files to BibTeX format files for inclusion in documents typeset using the LaTeX document processor. Try perldoc isi2bibtex for instructions, or read the script. This file generated on Wednesday 27th May 2003, from file '/home/evmik/dl/CIW.cgi', which has no subject line. @ARTICLE{FangXDJ03, author = {Fang, A. P. and Xu, H. L. and Dai, Z. W. and Jiang, Z. K.}, title = {Theoretical study of electromagnetically induced transparency in Er3+: YAlO3 crystal}, journal = {Physica B}, year = {2003}, volume = {328}, pages = {204-210}, abstract = {By using the density matrix theory of interaction between light and matter, and relevant parameter calculations of the relaxation rate, the dipole matrix elements and the ion density for a three-level ladder model, we have discussed theoretically the possibility to realize electromagnetically induced transparency (EIT) in Er3+:YA1O(3) crystal. (C) 2002 Elsevier Science B.V. All rights reserved. } } @ARTICLE{Xiao03, author = {Xiao, M.}, title = {Novel linear and nonlinear optical properties of electromagnetically induced transparency systems}, journal = {IEEE J. Sel. Top. Quantum Electron.}, year = {2003}, volume = {9}, pages = {86-92}, abstract = {We describe some interesting linear and nonlinear optical properties of three-level electromagnetically induced transparency (EIT) systems, such as absorption reduction, sharp dispersion change, and enhanced Kerr nonlinearity. These novel optical properties are very useful in enhancing efficient nonlinear optical processes, which can find applications in optoelectronic devices. We present some experiments done in our group in the past few years with three-level atomic systems, especially more recent experiments with EIT medium inside an optical cavity. } } @ARTICLE{WuWZ03, author = {Wu, Y. and Wen, L. L. and Zhu, Y. F.}, title = {Efficient hyper-Raman scattering in resonant coherent media}, journal = {Opt. Lett.}, year = {2003}, volume = {28}, pages = {631-633}, abstract = {We propose and analyze a hyper-Raman scheme for generation of coherent light in a five-level atomic system based on electromagnetically induced transparency (EIT). We show that EIT suppresses linear and nonlinear photon absorption and enables the hyper-Raman process to proceed through real, nearresonant intermediate states. The scheme greatly enhances hyper-Raman efficiency and may be used for generating short- wavelength radiation at low pump intensities. (C) 2003 Optical Society of America. } } @ARTICLE{LiS03, author = {Li, Y. F. and Sun, J. F.}, title = {Ultra-narrow electromagnetically induced transparency and inversionless gain in a ladder-four-level system}, journal = {Acta Phys. Sin.}, year = {2003}, volume = {52}, pages = {547-555}, abstract = {In this paper, we study the effects of Rabi frequencies and multi-path radiation on the electromagnetically induced transparency (EIT) and the inversionless gain in a ladder- four-level system driven by two-coherent fields. The Rabi frequencies of the field-driven transition from the upper level to middle levels play an important role for the realization of the ultra-narrow EIT and inversionless gain. Different excitation mechanism can change the position of the EIT. The action of the spontaneous alignment of the dipole moment is investigated. The explanation for the numerical results is presented using the theory of dressed state. } } @ARTICLE{PaternostroKH03, author = {Paternostro, M. and Kim, M. S. and Ham, B. S.}, title = {Generation of entangled coherent states via cross-phasemodulation in a double electromagnetically induced transparency regime}, journal = {Phys. Rev. A}, year = {2003}, volume = {67}, pages = {023811}, abstract = {The generation of an entangled coherent state is one of the most important ingredients of quantum information processing using coherent states. Recently, numerous schemes to achieve this task have been proposed. In order to generate travellingwave entangled coherent states, cross-phase-modulation, optimized by optical Kerr effect enhancement in a dense medium in an electromagnetically induced transparency (EIT) regime, seems to be very promising. In this scenario, we propose a fully quantized model of a double-EIT scheme recently proposed [D. Petrosyan and G. Kurizki, Phys. Rev. A 65, 33 833 (2002)]: the quantization step is performed adopting a fully Hamiltonian approach. This allows us to write effective equations of motion for two interacting quantum fields of light that show how the dynamics of one field depends on the photon-number operator of the other. The preparation of a Schrodinger cat state, which is a superposition of two distinct coherent states, is briefly exposed. This is based on nonlinear interaction via double EIT of two light fields (initially prepared in coherent states) and on a detection step performed using a 50:50 beam splitter and two photodetectors. In order to show the entanglement of an entangled coherent state, we suggest to measure the joint quadrature variance of the field. We show that the entangled coherent states satisfy the sufficient condition for entanglement based on quadrature variance measurement. We also show how robust our scheme is against a low detection efficiency of homodyne detectors. } } @ARTICLE{AgarwalD03, author = {Agarwal, G. S. and Dasgupta, S.}, title = {Laser-induced breakdown of the magnetic-field-reversal symmetry in the propagation of unpolarized light}, journal = {Phys. Rev. A}, year = {2003}, volume = {67}, pages = {023814}, abstract = {We show how a medium, under the influence of a coherent control field that is resonant or close to resonance to an appropriate atomic transition, can lead to very strong asymmetries in the propagation of unpolarized light when the direction of the magnetic field is reversed. We show how electromagnetically induced transparency (EIT) can be used in atomic vapor to mimic this magnetochiral effect that occurs in natural systems. EIT can produce much larger asymmetry than the well-known magnetochiral effect as we use the dipole-allowed transitions here. Using density-matrix calculations we present results for the breakdown of the magnetic-field-reversal symmetry for two different atomic configurations. } } @ARTICLE{GreentreeRVDdSM03, author = {Greentree, A. D. and Richards, D. and Vaccaro, J. A. and Durrant, A. V. and de Echaniz, S. R. and Segal, D. M. and Marangos, J. P.}, title = {Intensity-dependent dispersion under conditions of electromagnetically induced transparency in coherently prepared multistate atoms}, journal = {Phys. Rev. A}, year = {2003}, volume = {67}, pages = {023818}, abstract = {Interest in lossless nonlinearities has focussed on the dispersive properties of Lambda systems under conditions of electromagnetically induced transparency (EIT). We generalize the Lambda system by introducing further degenerate states to realize a "chain Lambda" atom where multiple coupling of the probe field significantly enhances the intensity-dependent dispersion without compromising the EIT condition. } } @ARTICLE{ZhuL02, author = {Zhu, K. D. and Li, W. S.}, title = {Electromagnetically induced transparency mediated by phonons in strongly coupled exciton-phonon systems}, journal = {Appl. Phys. B-Lasers Opt.}, year = {2002}, volume = {75}, pages = {861-864}, abstract = {It is shown theoretically that electromagnetically induced transparency (EIT), due to strong exciton-phonon coupling can occur in strongly coupled exciton-phonon systems such as polymers and organic semiconductors and lead to ultra-slow light effects. The results indicate that the strong coupling of excitons and phonons is important, but the excitonexciton interaction plays a small role in the generation of the EIT. Numerical results for polydiacetylene-toluene sulfonate are also presented. This EIT in a solid-state medium might be utilized for efficient multiwave mixing and quantum nondemolition measurements, as well as for novel acousto- optical devices. } } @ARTICLE{ZhangJSDW03, author = {Zhang, Y. L. and Jiang, L. and Sun, Z. R. and Ding, L. E. and Wang, Z. G.}, title = {Effect of four-wave mixing on electromagnetically induced transparency in Lambda-type system with a two-photon probe field}, journal = {Chin. Phys.}, year = {2003}, volume = {12}, pages = {174-177}, abstract = {Using density matrix equation, we calculate analytically as well as numerically the effect of the four-wave mixing (FWM) field on electromagnetically induced transparency (EIT) in the rubidium 5S(1/2)-5P(3/2)-5D(5/2) Lambda-type system with a twophoton probe field. The calculated results are in good agreement with Fulton's experimental results in 1995.} } @ARTICLE{ValenteFL03, author = {Valente, P. and Failache, H. and Lezama, A.}, title = {Temporal buildup of electromagnetically induced transparency and absorption resonances in degenerate two-level transitions}, journal = {Phys. Rev. A}, year = {2003}, volume = {67}, pages = {013806}, abstract = {The temporal evolution of electromagnetically induced transparency (EIT) and absorption (EIA) coherence resonances in pump-probe spectroscopy of degenerate two-level atomic transition is studied for light intensities below saturation. Analytical expressions for the transient absorption spectra are given for simple model systems and a model for the calculation of the time-dependent response of realistic atomic transitions, where the Zeeman degeneracy is fully accounted for, is presented. EIT and EIA resonances have a similar (opposite sign) time-dependent line shape, however, the EIA evolution is slower and thus narrower lines are observed for long interaction time. Qualitative agreement with the theoretical predictions is obtained for the transient probe absorption on the Rb-85 D-2 line in an atomic beam experiment. } } @ARTICLE{WuSZ03, author = {Wu, Y. and Saldana, J. and Zhu, Y. F.}, title = {Large enhancement of four-wave mixing by suppression of photon absorption from electromagnetically induced transparency}, journal = {Phys. Rev. A}, year = {2003}, volume = {67}, pages = {013811}, abstract = {We analyze a four-wave-mixing (FWM) scheme in a five-level atomic system based on electromagnetically induced transparency (EIT). We show that EIT suppresses both two-photon and threephoton absorptions in the FWM scheme and enables the four-wave mixing to proceed through real, resonant intermediate states without absorption loss. The scheme results in a several orders of magnitude increase in the FWM efficiency in comparison with a recent scheme [Phys. Rev. Lett. 88, 143902 (2002)] and may be used for generating short-wavelength radiation at low pump intensities. } } @ARTICLE{XuLBWG03, author = {Xu, J. H. and La Rocca, G. C. and Bassani, F. and Wang, D. and Gao, J. Y.}, title = {Electromagnetically induced one-photon and two-photon transparency in rubidium atoms}, journal = {Opt. Commun.}, year = {2003}, volume = {216}, pages = {157-164}, abstract = {We investigate electromagnetically induced transparency (EIT) for one-photon and resonant two-photon transitions in rubidium atomic vapors. One-photon transparency is obtained in the 5S5P-5D three level ladder system. At the same time, we study electromagnetically induced transparency in the two-photon transition (EITT) from the 5S to the 7S state resonant with the 5P intermediate state, when the latter is coupled to the 5D state by a control beam. The dependence of the transparency profile on the controlling laser intensity, linewidth, and detuning is investigated. Experimental results are obtained for isotopes Rb-85 and Rb-87 characterized by different hyperfine structures. Our findings for both the one-photon and the resonant two-photon transparency agree well with the prediction from three and four-level theory, respectively, with independently determined spectroscopic parameters. (C) 2002 Elsevier Science B.V. All rights reserved. } } @ARTICLE{KuznetsovaKHS02, author = {Kuznetsova, E. and Kocharovskaya, O. and Hemmer, P. and Scully, M. O.}, title = {Atomic interference phenomena in solids with a long-lived spin coherence}, journal = {Phys. Rev. A}, year = {2002}, volume = {66}, pages = {063802}, abstract = {We generalize the theory of electromagnetically induced transparency (EIT) and slow group velocity for the case of the homogeneous and inhomogeneous line broadening in both oneand two-photon transitions which unavoidably takes place in solid materials with a long-lived spin coherence. We identify regimes of EIT where the linewidth can be essentially reduced due to inhomogeneous broadening and, moreover, can be proportional to the amplitude of the driving field rather than the intensity. We suggest also a class of solid materials, namely, rare-earth ion doped semiconductors or dielectrics with electricdipole allowed transitions, that is very promising for realization and applications of EIT. } } @ARTICLE{PatnaikLH02, author = {Patnaik, A. K. and Liang, J. Q. and Hakuta, K.}, title = {Slow light propagation in a thin optical fiber via electromagnetically induced transparency}, journal = {Phys. Rev. A}, year = {2002}, volume = {66}, pages = {063808}, abstract = {We propose a configuration that utilizes electromagnetically induced transparency (EIT) to tailor a fiber mode propagating inside a thin optical fiber and coherently control its dispersion properties to drastically reduce the group velocity of the fiber mode. The key to this proposal is that the evanescent field of the thin fiber strongly couples with the surrounding active medium, so that the EIT condition is met by the medium. We show how the properties of the fiber mode are modified due to the EIT medium, both numerically and analytically. We demonstrate that the group velocity of the modified fiber mode can be drastically reduced (approximate to44 m/sec) using the coherently prepared orthohydrogen doped in a matrix of parahydrogen crystal as the EIT medium.} } @ARTICLE{JohnssonF02, author = {Johnsson, M. T. and Fleischhauer, M.}, title = {Quantum theory of resonantly enhanced four-wave mixing: Meanfield and exact numerical solutions}, journal = {Phys. Rev. A}, year = {2002}, volume = {66}, pages = {043808}, abstract = {We present a full quantum analysis of resonant forward fourwave mixing based on electromagnetically induced transparency (EIT). In particular, we study the regime of efficient nonlinear conversion with low-intensity fields that has been predicted from a semiclassical analysis. We derive an effective nonlinear interaction Hamiltonian in the adiabatic limit. In contrast to conventional nonlinear optics, this Hamiltonian does not have a power expansion in the fields and the conversion length decreases with decreasing input power. We analyze the stationary wave-mixing process in the forward scattering configuration using an exact numerical analysis for up to 10(3) input photons and compare the results with a mean- field approach. Due to quantum effects, complete conversion from the two pump fields into the signal and idler modes is achieved only asymptotically for large coherent pump intensities or for pump fields in few-photon Fock states. The signal and idler fields are perfectly quantum correlated which has potential applications in quantum communication schemes. We also discuss the implementation of a single-photon phase gate for continuous quantum computation. } } @ARTICLE{KryachkoLT02, author = {Kryachko, A. Y. and Litvak, A. G. and Tokman, M. D.}, title = {Electromagnetically induced transparency in high-temperature magnetoactive plasma}, journal = {J. Exp. Theor. Phys.}, year = {2002}, volume = {95}, pages = {697-704}, abstract = {We investigate a classical analog of electromagnetically induced transparency (EIT) currently popular in quantum electronics. We consider EIT for electron cyclotron waves in finite-temperature plasma. We derive an expression for the effective refractive index of an electromagnetic wave and study the dispersion and absorption of this wave under EIT conditions. Allowance for thermal motion is shown to radically change the behavior of the dispersion curves for the signal wave in the EIT region compared to the case of cold plasma. (C) 2002 MAIK "Nauka/Interperiodica". } } @ARTICLE{ThanopulosS02, author = {Thanopulos, I. and Shapiro, M.}, title = {Slowing down of light by laser induced barrier hopping}, journal = {J. Chem. Phys.}, year = {2002}, volume = {117}, pages = {8404-8411}, abstract = {We suggest that a very significant reduction in the group velocity of light occurs in a laser induced barrier-hopping process, known as "Laser Catalysis.'' In this process a system is made to hop over a potential barrier via a virtual transition to an excited bound state. As in electromagnetically induced transparency (EIT), the light absorption is predicted to dip to zero at a certain frequency, thereby also changing the refractive index, inducing in turn the slowing down of the group velocity of the light. In contrast to EIT, a single pulse is predicted to induce its own transparency and in contrast to self-induced transparency the process is predicted to be insensitive to the pulse area (as long as the pulse is intense enough to meet the adiabaticity criterion). Thus, the medium becomes transparent to the light, as the laser induced barrierhopping process brings about a fundamental change in the medium. (C) 2002 American Institute of Physics. } } @ARTICLE{AhufingerCCBMF02, author = {Ahufinger, V. and Corbalan, R. and Cataliotti, F. and Burger, S. and Minardi, F. and Fort, C.}, title = {Electromagnetically induced transparency in a Bose-Einstein condensate}, journal = {Opt. Commun.}, year = {2002}, volume = {211}, pages = {159-165}, abstract = {We report on the direct observation of the electromagnetically induced transparency (EIT) lineshape of cold Rb-87 atoms above and below the transition temperature for Bose-Einstein condensation (BEC). Similar results are observed in both temperature regimes, with an absorption reduction of about 60\%. Good agreement with a theoretical model is discussed. (C) 2002 Elsevier Science B.V. All rights reserved. } } @ARTICLE{MewesF02, author = {Mewes, C. and Fleischhauer, M.}, title = {Two-photon linewidth of light "stopping" via electromagnetically induced transparency}, journal = {Phys. Rev. A}, year = {2002}, volume = {66}, pages = {033820}, abstract = {We analyze the two-photon linewidth of a recently proposed adiabatic transfer technique for "stopping" of light using electromagnetically induced transparency (EIT). We show that a successful and reliable transfer of excitation from light to atoms and back can be achieved if the spectrum of the input probe pulse lies within the initial transparency window of EIT, and the two-photon detuning delta is less than the collective coupling strength (collective vacuum Rabi frequency) grootN divided by rootgammaT, with gamma being the radiative decay rate, N being the effective number of atoms in the sample, and T being the pulse duration. Hence in an optically thick medium light "storage" and retrieval is possible with high fidelity even for systems with rather large two-photon detuning or inhomogeneous broadening. } } @ARTICLE{LiNS02, author = {Li, Y. F. and Niu, Y. P. and Sun, J. F.}, title = {The effect of resonant four-wave-mixing on electromagnetically induced transparency in Lambda-type system employing a twophoton field}, journal = {Phys. Lett. A}, year = {2002}, volume = {301}, pages = {195-202}, abstract = {Four-wave-mixing has been considered in a A-type system to make clear the asymmetry occurred in EIT profile which had been realized experimentally in Phys. Rev. A 52 (1995) 2302. We present both analytical and numerical calculation to explain the reason. In the case of Doppler-free for the two-photon probe field, why EIT dip was not detected is also been demonstrated. (C) 2002 Elsevier Science B.V. All rights reserved. } } @ARTICLE{ShvetsW02, author = {Shvets, G. and Wurtele, J. S.}, title = {Transparency of magnetized plasma at the cyclotron frequency}, journal = {Phys. Rev. Lett.}, year = {2002}, volume = {89}, pages = {115003}, abstract = {Electromagnetic radiation is strongly absorbed by a magnetized plasma if the radiation frequency equals the cyclotron frequency of plasma electrons. It is demonstrated that absorption can be completely canceled in the presence of a magnetostatic field of an undulator, or a second radiation beam, resulting in plasma transparency at the cyclotron frequency. This effect is reminiscent of the electromagnetically induced transparency (EIT) of three-level atomic systems, except that it occurs in a completely classical plasma. Unlike the atomic systems, where all the excited levels required for EIT exist in each atom, this classical EIT requires the excitation of nonlocal plasma oscillation. A Lagrangian description was used to elucidate the physics of the plasma transparency and control of group and phase velocity. This control leads to applications for electromagnetic pulse compression and electron/ion acceleration. } } @ARTICLE{JavanKLS02, author = {Javan, A. and Kocharovskaya, O. and Lee, H. and Scully, M. O.}, title = {Narrowing of electromagnetically induced transparency resonance in a Doppler-broadened medium}, journal = {Phys. Rev. A}, year = {2002}, volume = {66}, pages = {013805}, abstract = {We derive an analytic expression for the linewidth of electromagnetically induced transparency (EIT) resonance in a Doppler-broadened system. It is shown here that for relatively low intensity of the driving field the EIT linewidth is proportional to the square root of intensity and is independent of the Doppler width, similar to the laser-induced line narrowing effect described by Feld and Javan. In the limit of high intensity we recover the usual power-broadening case where the EIT linewidth is proportional to the intensity and inversely proportional to the Doppler width. } } @ARTICLE{DengHKAP02, author = {Deng, L. and Hagley, E. W. and Kozuma, M. and Akamatsu, D. and Payne, M. G.}, title = {Achieving very-low-loss group velocity reduction without electromagnetically induced transparency}, journal = {Appl. Phys. Lett.}, year = {2002}, volume = {81}, pages = {1168-1170}, abstract = {A Raman method is studied experimentally for potential opticalwave group velocity reduction in resonant medium. Specifically, we show that the proposed method can achieve significant group velocity reduction comparable to the conventional electromagnetically induced transparency (EIT) method that had been exclusively used to date. In addition, we show that this method has a significantly lower loss compared to the EIT method, and has rich dynamics such as probe pulse narrowing. Such features have applications in the domain of telecommunication technology. (C) 2002 American Institute of Physics. } } @ARTICLE{ArtoniBCL02, author = {Artoni, M. and Bassani, F. and Carusotto, I. and La Rocca, G. C.}, title = {The regime of electromagnetically induced transparency in optically dense media: from atoms to excitons}, journal = {Braz. J. Phys.}, year = {2002}, volume = {32}, pages = {275-283}, abstract = {The phenomenon of electromagnetically induced transparency (EIT) was discovered by Adriano Gozzini and coworkers in 1976 in Pisa. Novel schemes to investigate and exploit EIT in the optical domain have attracted much interest both in atomic and solid state systems. We discuss some of our recent theoretical results, in particular: i) a well developed EIT regime based on free exciton levels in undoped bulk crystalline Cu2O; ii) light dragging effects in moving media under EIT; iii) the coherent control of Cherenkov radiation in the EIT regime. } } @ARTICLE{ZhaoWXZYJ02, author = {Zhao, J. M. and Wang, L. R. and Xiao, L. T. and Zhao, Y. T. and Yin, W. B. and Jia, S. T.}, title = {Experimental measurement of absorption and dispersion in V-type cesium atom}, journal = {Opt. Commun.}, year = {2002}, volume = {206}, pages = {341-345}, abstract = {Electromagnetically induced transparency (EIT) is observed in a three-level V-type system in cesium vapor at room temperature. The absorption and dispersion properties are measured under the condition that the coupling frequency is exactly resonance with transition 6S(1,2) (F = 4) to 6P(3,2) (F' = 3) while the probe frequency is scanned across the transitions from the 6S(1,2) (F = 4) to all structures of the 6P(3,2). The effects of detuning of the coupling beam are studied. The results of the experiment agree with the simple theoretical analysis. (C) 2002 Published by Elsevier Science B.V. } } @ARTICLE{WuG02, author = {Wu, J. H. and Gao, J. Y.}, title = {Absorption properties of a driven Doppler-broadened ladder system with hyperfine structure}, journal = {Chin. Phys.}, year = {2002}, volume = {11}, pages = {572-577}, abstract = {We have studied the absorption spectrum of a Doppler-broadened ladder system, where the highest level is coupled into two middle hyperfine sublevels by a strong coherent field. We find that, when the system is considered as homogeneous, either two or three spectral components are observed, depending on the detuning of the coherent field. But when the velocity distribution of atoms is considered, we can always observe one electromagnetically induced transparency (EIT) window with high dispersion. So the atomic hyperfine structure cannot be an impediment for obtaining FIT. } } @ARTICLE{DengHKP02, author = {Deng, L. and Hagley, E. W. and Kozuma, M. and Payne, M. G.}, title = {Optical-wave group-velocity reduction without electromagnetically induced transparency}, journal = {Phys. Rev. A}, year = {2002}, volume = {65}, pages = {051805}, abstract = {A Raman scheme for optical-pulse group-velocity reduction in a pure lifetime broadened system is studied. We show that this nonelectromagnetically induced transparency (NEIT) scheme has many advantages over the conventional method that critically relies on the transparency window created by an EIT process. Significant reduction of the group velocity, probe field loss, and pulse distortion are reported. In addition, rich dynamics of the propagation process are studied. } } @ARTICLE{CardimonaH02, author = {Cardimona, D. A. and Huang, D. H.}, title = {Connection of off-diagonal radiative-decay coupling to electromagnetically induced transparency and amplification without inversion in a three-level atomic system}, journal = {Phys. Rev. A}, year = {2002}, volume = {65}, pages = {033828}, abstract = {The equivalence between the off-diagonal radiative-decay coupling (ODRDC) effect in the bare-atom picture of a threelevel atomic system [see Cardimona et al., J. Phys. B 15, 55 (1982)] and the electromagnetically induced transparency (EIT) effect in the dressed-atom picture [see Imamoglu et al., Opt. Lett. 14, 1344 (1989)] is uncovered and a full comparison of their physical origins is given. The mechanism for both ODRDC and Harris' EIT is found to be a consequence of the quantum interference between a direct absorption path and an indirect absorption path mediated by either a self absorption of spontaneous photons or a Fano-type coupling. A connection is then pointed out between the effects of probe-field gain (PFG) based on an ODRDC process [see Huang et al., Phys. Rev. A 64, 013822 (2001)] and amplification without inversion (AWI) [see Fearn et al., Opt. Commun. 87, 323 (1992)] in the bare-atom picture of a three-level atomic system. The PFG effect is found as a result of transferring electrons between the two upper levels due to the phase-sensitive coherence provided by a laser-induced ODRDC process, while the AWI effect to one of the two probe fields is attributed to its coupling to a strong laser field generating an off-resonant gain through an induced nonlinearity in the other probe field. Both the advantages and disadvantages as well as the limitations of the ODRDC, EIT, PFG, and AWI effects are discussed and compared. } } @ARTICLE{BadgerHA01, author = {Badger, S. D. and Hughes, I. G. and Adams, C. S.}, title = {Hyperfine effects in electromagnetically induced transparency}, journal = {J. Phys. B-At. Mol. Opt. Phys.}, year = {2001}, volume = {34}, pages = {L749-L756}, abstract = {The role of hyperfine structure in electromagnetically induced transparency (EIT) is investigated by studying the 5S(1/2)- 5P(3/2)-5D(3/2,5/2) cascade system in Rb-85 and Rb-87. We show that if the hyperfine splitting Delta(hfs) is larger than the Rabi frequency of the coupling beam, Q, then the observed EIT spectra can be modelled by adding terms corresponding to each hyperfine state. However, in the strong-coupling limit, Omega(c) much greater than Delta(hfs), a complete multilevel description is required. } } @ARTICLE{AffolderbachKWTY02, author = {Affolderbach, C. and Knappe, S. and Wynands, R. and Taichenachev, A. V. and Yudin, V. I.}, title = {Electromagnetically induced transparency and absorption in a standing wave}, journal = {Phys. Rev. A}, year = {2002}, volume = {65}, pages = {043810}, abstract = {A thermal vapor of three-level atoms irradiated by two copropagating laser beams of suitable frequencies exhibits the phenomenon of coherent population trapping, leading to an electromagnetically induced transparency (EIT). When a mirror reflects the beams back onto themselves one finds that depending on the position along the resulting standing wave the fluorescence intensity from the sample (cesium in our case) decreases (EIT) or even increases [electromagnetically induced absorption (EIA)] with a period on the centimeter scale. An intuitive picture is based on the interference of coherent dark states but the explanation of the EIA effect requires consideration of Doppler effects in the thermal vapor. This allows for a quantitative comparison between experimental and calculated results. } } @ARTICLE{XuDJ02, author = {Xu, H. L. and Dai, Z. W. and Jiang, Z. K.}, title = {Effect of concentration of the Er3+ ion on electromagnetically induced transparency in Er3+: YAG crystal}, journal = {Phys. Lett. A}, year = {2002}, volume = {294}, pages = {19-25}, abstract = {We studied the effect of Er3+ concentration on electromagnetically induced transparency in two types of three- level schemes-the ladder and the A models in Er3+:YAG, The numerical calculations show that, under the same intensities of the probe and the coupling fields, the absorption and the dispersion were dramatically changed with Er3+ concentration. (C) 2002 Elsevier Science B.V. All rights reserved. } } @ARTICLE{LitvakT02, author = {Litvak, A. G. and Tokman, M. D.}, title = {Electromagnetically induced transparency in ensembles of classical oscillators}, journal = {Phys. Rev. Lett.}, year = {2002}, volume = {88}, pages = {095003}, abstract = {We develop a classical model of the parametric effect of electromagnetically induced transparency (EIT) within the line of resonance absorption of an electromagnetic wave in the medium-an effect initially discovered for a quantum three-level system. On the basis of this model, the EIT effect for electromagnetic waves at frequencies of the electron-cyclotron resonance in a cold plasma is considered. Similar to the analogous quantum scheme, the EIT window in the classical model is characterized by group deceleration of the reference electron-cyclotron wave. } } @ARTICLE{SorokinG02, author = {Sorokin, P. P. and Glownia, J. H.}, title = {Lasers without inversion (LWI) in Space: A possible explanation for intense, narrow-band, emissions that dominate the visible and/or far-UV (FUV) spectra of certain astronomical objects}, journal = {Astron. Astrophys.}, year = {2002}, volume = {384}, pages = {350-363}, abstract = {The optical or far-UV (FUV) spectra of certain objects in Space are completely dominated by one or two spectrally narrow emission lines, strongly suggesting that laser action of some kind occurs in these objects. However, the electronic level structures of the atoms/ions producing these emissions preclude the possibility of maintaining population inversions on the electronic transitions involved. In lasers, gain is normally produced on an optical transition that is inverted, i.e. one that has more atoms maintained in the upper than in the lower state, so that stimulated emission can exceed stimulated absorption. However, as a result of discoveries made in quantum electronics over the past 30 years or so, one now knows that there are several ways to make stimulated emission occur on a transition that is not inverted, i.e. to realize a "laser without inversion (LWI)". This requires first making the atoms non-absorbing at the lasing frequency, i.e. setting up a condition of "electromagnetically induced transparency (EIT)". Some recently developed EIT techniques for three-level atoms are first reviewed. A simple model for a space LWI based upon a gas of two-level atoms is then proposed. In this model, transparency results from a form of EIT induced by the presence of an intense, monochromatic, continuous-wave, laser beam tuned to the frequency omega(o) of the two-level-atom transition. Amplification of light at this same frequency occurs via resonant stimulated hyper-Raman scattering (SHRS) and four-wave mixing (FWM), with pumping energy provided by continuum starlight spectrally overlapping the two outer absorption sidebands ("Mollow bands") induced by the presence of the beam at omega(o). Two specific examples of superintense line emission from Space are here considered. These are (a) the H(alpha) emission line appearing as a dominant singularity in certain reddened, early-type stars, and (b) the powerful O VI (1032 Angstrom, 1038 Angstrom) emission doublet that dominates the FUV emission spectra of symbiotic stars such as RR Tel.} } @ARTICLE{JuzeliunasC02, author = {Juzeliunas, G. and Carmichael, H. J.}, title = {Systematic formulation of slow polaritons in atomic gases}, journal = {Phys. Rev. A}, year = {2002}, volume = {65}, pages = {021601}, abstract = {We formulate a theory of slow polaritons in atomic gases and apply it to the slowing down, storing, and redirecting of laser pulses in an electromagnetically induced transparency (EIT) medium. The normal modes of the coupled matter and radiation are determined through a full diagonalization of the dissipationless Hamiltonian. Away from the EIT resonance, where the polaritons acquire an excited-state contribution, lifetimes are introduced as a secondary step. With detuning included various four-wave mixing possibilities are analyzed. We investigate specifically the possibility of reverting a stopped polariton by reversing the control beam. } } @ARTICLE{ValenteFL02, author = {Valente, P. and Failache, H. and Lezama, A.}, title = {Comparative study of the transient evolution of Hanle electromagnetically induced transparency and absorption resonances}, journal = {Phys. Rev. A}, year = {2002}, volume = {65}, pages = {023814}, abstract = {The temporal evolutions of electromagnetically induced transparency (EIT) and absorption (EIA) were observed in a Hanle absorption experiment carried on the D-2 lines Of Rb-87 vapor by suddenly turning the magnetic field on or off. The main features of the experimental observations are well reproduced by a theoretical model based on Bloch equation where the atomic level degeneracy has been fully accounted for. Similar (opposite phase) evolutions were observed at low optical-field intensities for Hanle-EIT or Hanle-EIA resonances. Unlike the Hanle-EIA transients that are increasingly shorter for driving field intensities approaching saturation, the B not equal 0 transient of the Hanle-EIT signal at large driving field intensities present a long decay time approaching the atomic transit time. Such counterintuitive behavior is interpreted as a consequence of the Zeno effect.} } @ARTICLE{LiSZW02, author = {Li, Y. F. and Sun, J. F. and Zhang, X. Y. and Wang, Y. C.}, title = {Laser-induced double-dark resonances and double-transparencies in a four-level system}, journal = {Opt. Commun.}, year = {2002}, volume = {202}, pages = {97-102}, abstract = {We study the generations of dark resonance and electomagnetically induced transparency (EIT) effects in the four-level system with two coherent fields coupling the transition from upper level to a pair of ground levels and a lower excited state. The quantum interference between two excited pathways results in double-dark resonances and doubletransparency holes with adjustable frequencies driven into the absorption spectrum in the atomic system. A clear analytical explanation for our numerical results is presented. It is shown that the relation of detunings of two coherent fields plays an important role in the generations of the coherent population trapping and EIT effects. (C) 20021 Elsevier Science B.V. All rights reserved. } } @ARTICLE{WangGX02, author = {Wang, H. and Goorskey, D. J. and Xiao, M.}, title = {Atomic coherence induced Kerr nonlinearity enhancement in Rb vapour}, journal = {J. Mod. Opt.}, year = {2002}, volume = {49}, pages = {335-347}, abstract = {The Kerr nonlinear index of refraction for rubidium atoms is measured by using an optical ring cavity with and without electromagnetically induced transparency (EIT). Significant enhancement and inhibition of the Kerr nonlinear index is observed near resonance with EIT. The nonlinear index of refraction is measured as functions of probe and coupling frequency detunings, respectively, with and without the presence of EIT. A simple theoretical calculation including Doppler broadening is presented and is found to be in good qualitative agreement with the experimentally measured results.} } @ARTICLE{MatskoNW02, author = {Matsko, A. B. and Novikova, I. and Welch, G. R.}, title = {Radiation trapping under conditions of electromagnetically induced transparency}, journal = {J. Mod. Opt.}, year = {2002}, volume = {49}, pages = {367-378}, abstract = {Reabsorption of spontaneously emitted photons, or radiation trapping, is a process that occurs when light interacts with optically thick media. It is shown, both theoretically and experimentally, that this effect in optically thick atomic vapour leads to a decrease in transmission of coherent laser radiation propagating under conditions of electromagnetically induced transparency (EIT). A simple theory is developed taking into account the radiation trapping, which is in a good agreement with the experimental observations and exact numerical simulation. This allows better understanding of the physics of EIT in general, and properties of dense coherent atomic media in particular. } } @ARTICLE{HussKW02, author = {Huss, A. F. and Korsunsky, E. A. and Windholz, L.}, title = {Phase control of electromagnetically induced transparency in a double-Lambda system}, journal = {J. Mod. Opt.}, year = {2002}, volume = {49}, pages = {141-155}, abstract = {It is experimentally demonstrated that the effect of electromagnetically induced transparency (EIT) can be controlled through the radiation phases. Corresponding investigations are performed by exciting a sodium atomic vapour by four-frequency laser radiation in a double-A configuration. In such a system the nonabsorbing (dark) state, responsible for EIT, is created only for particular values of the relative radiation phase. This phase dependency is confirmed using three different methods of phase control. Additionally, the relative phase is set at defined values in order to adjust the medium to a fixed transmission behaviour. } } @ARTICLE{WangZ02, author = {Wang, K. G. and Zhu, S. Y.}, title = {Atomic storage states}, journal = {Chin. Phys. Lett.}, year = {2002}, volume = {19}, pages = {56-59}, abstract = {We present a complete description of atomic storage states which may appear in the electromagnetically induced transparency (EIT). The result shows that the spatial coherence has been included in the atomic collective operators and the atomic storage states. In some limits, a set of multimode atomic storage states has been established in correspondence with the multimode Fock states of the electromagnetic field. This gives a better understanding of the fact that, in EIT, the optical coherent information can be preserved and recovered.} } @ARTICLE{AlzarMN02, author = {Alzar, C. L. G. and Martinez, M. A. G. and Nussenzveig, P.}, title = {Classical analog of electromagnetically induced transparency}, journal = {Am. J. Phys.}, year = {2002}, volume = {70}, pages = {37-41}, abstract = {We present a classical analog of electromagnetically induced transparency (EIT). In a system of just two coupled harmonic oscillators subject to a harmonic driving force, we reproduce the phenomenology observed in EIT. We also describe a simple experiment with two linearly coupled RLC circuits which can be incorporated into an undergraduate laboratory. (C) 2002 American Association of Physics Teachers. } } @ARTICLE{ZhuL01, author = {Zhu, K. D. and Li, W. S.}, title = {Electromagnetically induced transparency due to exciton-phonon interaction in an organic quantum well}, journal = {J. Phys. B-At. Mol. Opt. Phys.}, year = {2001}, volume = {34}, pages = {L679-L686}, abstract = {Using the bosonic exciton approximation, we show that there exists electromagnetically induced transparency (EIT) in an organic quantum well which includes the interaction of charge- transfer excitons and phonons. The numerical results indicate that the strong exciton-phonon interaction plays a key role in the generation of the EIT. Without the exciton-phonon coupling, the EIT will disappear immediately. Ultraslow light effects are also discussed in this system. } } @ARTICLE{Kofman01, author = {Kofman, A. G.}, title = {Electromagnetically induced transparency and evolution of a two-level system under chaotic field of arbitrary intensity}, journal = {Eur. Phys. J. D}, year = {2001}, volume = {17}, pages = {153-165}, abstract = {The electromagnetically induced transparency (EIT) with a (near-)resonant chaotic (amplitude-phase fluctuating, GaussianMarkovian) coupling field is studied theoretically. The Fourier transform of the steady-state EIT spectrum, which determines a nonstationary probe absorption, is also considered. This quantity equals the average diagonal element of the (reduced) evolution operator of the coupled transition (the evolution function). The exact solution in the form of a continued fraction is obtained and used to perform numerical calculations. Moreover, a number of approximate analytical results are obtained, which, together with the results of previous publications, describe the EIT and the evolution function in all possible regimes. In particular, in the constructive-interference case the EIT increases with the coupling-field bandwidth v at sufficiently small v. For a strong field, the maximum of the transparency as a function of v is less than that for a monochromatic field of the same average intensity. In contrast, for a weak field, there is a range of v values, where the field fluctuations do not affect the EIT. The latter result is shown to hold for a broad class of stochastic fields. } } @ARTICLE{Windholz01, author = {Windholz, L.}, title = {Coherent population trapping in multi-level atomic systems}, journal = {Phys. Scr.}, year = {2001}, volume = {T95}, pages = {81-91}, abstract = {Coherent population trapping (CPT) is treated in multi-level systems, excited by twoor four-frequency laser light. The dynamics of filling non-absorbing (dark) states is investigated. In cases where all transitions involved are excited (closed systems), the effect becomes dependent on the relative phase of the light waves. Further electromagnetically induced transparency (EIT) is described in three- and four- level systems and used for effective side band generation.} } @ARTICLE{BhatiaWS01, author = {Bhatia, P. S. and Welch, G. R. and Scully, M. O.}, title = {Laser amplification without population inversion on the D-1 line of the Cs atom with semiconductor diode lasers}, journal = {J. Opt. Soc. Am. B-Opt. Phys.}, year = {2001}, volume = {18}, pages = {1587-1596}, abstract = {The importance of lasing without inversion (LWI) in comparison with the use of nonlinear optical techniques and techniques based on high-intensity femtosecond light pulses to generate high-frequency coherent radiation is outlined, The original development and utilization of an experimental facility based on semiconductor diode lasers to study the fundamental aspects of LWI on the D-1 line of the Cs atom, which is rarely attempted, is described. This experimental facility is used to observe inversionless amplification on the D-1 line of the Cs atom by use of a A atomic scheme, A combination of EIT and broadband pumping of atoms from the lower to the upper level of the probe transition allowed the observation of the inversionless gain. Justification for the absence of inversion in the probe transition is provided. We report a single-pass inversionless gain of approximate to 11\% with relatively weak incoherent pumping. The results show improvement over the previously reported inversionless gain observed in Na, Rb, and Cs, illustrating the potential advantage of using the D-1 line of Cs. (C) 2001 Optical Society of America. } } @ARTICLE{ChenLCSY01, author = {Chen, C. Y. and Liao, Y. A. and Chiu, H. Y. and Su, J. J. and Yu, I. A.}, title = {Observation of the quantum interference phenomenon induced by interacting dark resonances}, journal = {Phys. Rev. A}, year = {2001}, volume = {6405}, pages = {053806}, abstract = {We report an experimental observation of narrow and highcontrast spectra. which are induced by interacting dark resonances and have been predicted in Phys. Rev. A 60, 3225 (1999). Spectra are measured with cold Rb-87 atoms produced by a magneto-optical trap. In this experimental system, a coupling laser and a weak probe laser form a three-level Lambda -type configuration of electromagnetically induced transparency (EIT); a microwave drives a magnetic-dipole transition between the fourth level and the ground state that is coupled with the excited state by the coupling laser. The observed spectral profile of probe absorption exhibits a very sharp peak emerging inside a narrow EIT dip. Such spectral feature provides more opportunities in manipulating atomic-optical response.} } @ARTICLE{OpatrnyW01, author = {Opatrny, T. and Welsch, D. G.}, title = {Cross phase modulation enhancement by coupled cavities and electromagnetically induced transparency}, journal = {Fortschritte Phys.-Prog. Phys.}, year = {2001}, volume = {49}, pages = {1065-1070}, abstract = {We propose an optical double-cavity resonator whose response to a signal is similar to that observed in electromagnetically induced transparency (EIT). A combination of such a device with a four-level EIT medium can serve for achieving large crossKerr modulation of a probe field by a signal field. } } @ARTICLE{Ichimura01, author = {Ichimura, K.}, title = {A simple frequency-domain quantum computer with ions in a crystal coupled to a cavity mode}, journal = {Opt. Commun.}, year = {2001}, volume = {196}, pages = {119-125}, abstract = {A quantum computer where quantum bits (qubits) are defined in frequency domain and interaction between qubits is mediated by a single cavity mode is proposed. In this quantum computer, qubits can be individually addressed regardless of their positions. Therefore, randomly distributed systems in space can be directly employed as qubits. An application of nuclear spins in rare-earth ions in a crystal for the quantum computer is quantitatively analyzed. (C) 2001 Elsevier Science B.V. All rights reserved. } } @ARTICLE{OpatrnyW01, author = {Opatrny, T. and Welsch, D. G.}, title = {Coupled cavities for enhancing the cross-phase-modulation in electromagnetically induced transparency}, journal = {Phys. Rev. A}, year = {2001}, volume = {6402}, pages = {023805}, abstract = {We propose an optical double-cavity resonator whose response to a signal is similar to that of an electromagnetically induced transparency (EIT) medium. A combination of such a device with a four-level EIT medium can serve for achieving large cross- Kerr modulation of a probe field by a signal field. This would offer the possibility of building a quantum logic gate based on photonic qubits. We discuss the technical requirements that are necessary for realizing a probe-photon phase shift of pi caused by a single-photon signal. The main difficulty is the requirement of an ultralow reflectivity beam splitter, and we must be able to operate a sufficiently dense cool EIT medium in a cavity. } } @ARTICLE{ClarkevC01, author = {Clarke, J. J. and van Wijngaarden, W. A. and Chen, H. X.}, title = {Electromagnetically induced transparency using a vapor cell and a laser-cooled sample of cesium atoms}, journal = {Phys. Rev. A}, year = {2001}, volume = {6402}, pages = {023818}, abstract = {Electromagnetically induced transparency (EIT) was observed in a mismatched-wavelength cascade system using a room temperature vapor cell and laser-cooled atoms. A cw probe laser beam monitored the cesium 6S(1/2)----6P(3/2) transition while another cw laser coupled the 6P(3/2) state to a higher excited state. The ratio of the observed Rabi frequencies for coupling to the 6P(3/2)--> (11-13)D-3/2,(5/2) transitions agreed closely with that predicted using the transition oscillator strengths. A comparison of the EIT signals obtained using cold atoms and the vapor cell is made. } } @ARTICLE{KimKMPK01, author = {Kim, K. and Kwon, M. and Moon, H. S. and Park, H. D. and Kim, J. B.}, title = {Measurements of normal and anomalous dispersions in coherently driven Cs vapors}, journal = {J. Korean Phys. Soc.}, year = {2001}, volume = {38}, pages = {666-669}, abstract = {Negative and positive dispersions in transitions of the C-S D-2 line have been measured by setting up a homodyne Mach-Zehnder interferometer through a coherently driven atomic system. Anomalous dispersion due to the electromagnetically induced absorption (EIA) process and normal dispersion due to the electromagnetically induced transparency (EIT) process were dn/d v similar or equal to -1.8 x 10-(14) Hz(-1) and 8.7 x 10- (14) Hz(-1), which corresponded to a negative group velocity v(g) similar or equal to -c/14 and a positive one v(g) similar or equal to c/31, respectively. } } @ARTICLE{YanRZ01, author = {Yan, M. and Rickey, E. G. and Zhu, Y. F.}, title = {Nonlinear absorption by quantum interference in cold atoms}, journal = {Opt. Lett.}, year = {2001}, volume = {26}, pages = {548-550}, abstract = {We report an experimental observation of third-order nonlinear absorption by quantum interference in Rb-87 atoms cooled and confined in a magneto-optic trap. A coupling laser creates electromagnetically induced transparency (EIT) in a multilevel Rb system in which the third-order nonlinear absorption is enhanced by constructive quantum interference while the linear absorption is inhibited by destructive interference. Our experiment demonstrates the EIT system proposed by Harris and Yamamoto [Phys. Rev. Lett. 81, 3611 (1998)], which absorbs two photons but not one photon in the dressed-state picture. (C) 2001 Optical Society of America. } } @ARTICLE{McGloinFD01, author = {McGloin, D. and Fulton, D. J. and Dunn, M. H.}, title = {Electromagnetically induced transparency in N-level cascade schemes}, journal = {Opt. Commun.}, year = {2001}, volume = {190}, pages = {221-229}, abstract = {We examine electromagnetically induced transparency (EIT) in cascade schemes with N levels and N - 1 fields. We show that transparency effects are present when N is odd and that destruction of EIT is present on line centre when N is even. We predict multiple dark resonances in such schemes due to multiphoton EIT effects. By examining atomic rubidium we propose methods of achieving such schemes by use of coupling rf fields into hyperfine levels. (C) 2001 Published by Elsevier Science B.V. } } @ARTICLE{ArtoniCLB01, author = {Artoni, M. and Carusotto, I. and La Rocca, G. C. and Bassani, F.}, title = {Fresnel light drag in a coherently driven moving medium}, journal = {Phys. Rev. Lett.}, year = {2001}, volume = {86}, pages = {2549-2552}, abstract = {We theoretically study how the phase of a light plane wave propagating in a resonant medium under electromagnetically induced transparency (EIT) is affected by the uniform motion of the medium. For cuprous oxide (Cu2O), where EIT can be implemented through a typical pump-probe configuration, the resonant probe beam experiences a phase shift (Fresnel-Fizeau effect) that may vary over a wide range of values, positive or negative, and even vanishing, due to the combined effects of the strong frequency dispersion and anisotropy both induced by the pump. The use of such a coherently driven dragging medium may improve by at least 1 order of magnitude the sensitivity at low velocity in optical drag experiments. } } @ARTICLE{BenninkBSW01, author = {Bennink, R. S. and Boyd, R. W. and Stroud, C. R. and Wong, V.}, title = {Enhanced self-action effects by electromagnetically induced transparency in the two-level atom}, journal = {Phys. Rev. A}, year = {2001}, volume = {6303}, pages = {033804}, abstract = {Electromagnetically induced transparency (EIT) has been studied primarily within the context of multilevel atomic systems. We show that EIT can occur also in a two-level atomic system and can lead to strong self-action and slow-light effects that are not hampered by material absorption, with important potential implications for processes such as squeezed-light generation and the propagation of optical solitons. } } @ARTICLE{Kofman01, author = {Kofman, A. G.}, title = {Electromagnetically induced transparency and evolution of a two-level system under a strong chaotic field}, journal = {Phys. Rev. A}, year = {2001}, volume = {6303}, pages = {033810}, abstract = {The present paper treats the electromagnetically induced transparency (EIT), i.e., the absorption spectrum of a weak probe field, near-resonant to a material transition, in the presence of a strong amplitude-phase fluctuating field which couples the upper level of the transition to another excited level. The coupling field is assumed to be chaotic (i.e., a complex Gaussian process with a Lorentzian spectrum) and so strong that the material relaxation and the detuning can be neglected. In addition, we consider the Fourier transform of the spectrum (U) over bar (aa)(t), which determines absorption of a probe field with a time-dependent intensity. The quantity (U) over bar (aa)(t) equals a diagonal element of the average reduced evolution operator of the two-level system (TLS), coupled by the strong field. As a starting point, we use the stationary, partially averaged stochastic Schrodinger equation, which has the form of a set of two second-order differential equations. The theory is developed by combining analytical and numerical approaches. For the most important regime, when the rms Rabi frequency V-0 is much greater than the coupling-held bandwidth nu, we obtain scaling relations for the EIT line shape and the TLS evolution. In particular, the absorption at the minimum (i.e., at the resonance frequency) scales as nu V1/3(0)-4/3, whereas the evolution function (U) over bar (aa)(t) performs damped oscillations with the decay rate on the order of (V(0)(2)nu)(1/3). These results differ significantly from those following from the uncorrelated-jump model. The results of this paper are shown to be applicable to more general models of amplitude-phase fluctuations than the Gaussian-Markovian chaotic field. } } @ARTICLE{KocharovskayaRS01, author = {Kocharovskaya, O. and Rostovtsev, Y. and Scully, M. O.}, title = {Stopping light via hot atoms}, journal = {Phys. Rev. Lett.}, year = {2001}, volume = {86}, pages = {628-631}, abstract = {We prove that it is possible to freeze a light pulse (i.e., to bring it to a full stop) or even to make its group velocity negative in a coherently driven Doppler broadened atomic medium via electromagnetically induced transparency (EIT). This remarkable phenomenon of the ultraslow EIT polariton is based on the spatial dispersion of the refraction index n(w,k), i.e., its wave number dependence, which is due to atomic motion and provides a negative contribution to the group velocity. This is related to, but qualitatively different from, the recently observed light slowing caused by large temporal (frequency) dispersion. } } @ARTICLE{ScullyAKKM01, author = {Scully, M. O. and Agarwal, G. S. and Kocharovskaya, O. and Kozlov, V. V. and Matsko, A. B.}, title = {Mixed electromagnetically and self-induced transparency}, journal = {Opt. Express}, year = {2001}, volume = {8}, pages = {66-75}, abstract = {We show that application of self-induced transparency (SIT) solitons as a driving field in V-type electromagnetically induced transparency (EIT) leads to "mixed induced transparency" (MIT) that nicely combines the best features of both SIT and EIT. (C) 2001 Optical Society of America.} } @ARTICLE{WangGBX00, author = {Wang, H. and Goorskey, D. J. and Burkett, W. H. and Xiao, M.}, title = {Cavity-linewidth narrowing by means of electromagnetically induced transparency}, journal = {Opt. Lett.}, year = {2000}, volume = {25}, pages = {1732-1734}, abstract = {Cavity-linewidth narrowing in a ring cavity that is due to the high dispersion and reduced absorption produced by electromagnetically induced transparency (EIT) in rubidium-atom vapor has been experimentally observed. The cavity linewidth with rubidium atoms under EIT conditions can be significantly narrowed. Cavity-linewidth narrowing was measured as a function of coupling beam power. (C) 2000 Optical Society of America.} } @ARTICLE{KosachiovK00, author = {Kosachiov, D. V. and Korsunsky, E. A.}, title = {Efficient microwave-induced optical frequency conversion}, journal = {Eur. Phys. J. D}, year = {2000}, volume = {11}, pages = {457-463}, abstract = {Frequency conversion process is studied in a medium of atoms with a Lambda configuration of levels, where transition between two lower states is driven by a microwave field. In this system, conversion efficiency can be very high by virtue of the effect of electromagnetically induced transparency (EIT). Depending on intensity of the microwave field, two regimes of EIT are realized: "dark-state" EIT for the weak field, and Autler-Townes-type EIT for the strong one. We study both cases via analytical and numerical solution and find optimum conditions for the conversion. } } @ARTICLE{GordonMJ00, author = {Gordon, D. F. and Mori, W. B. and Joshi, C.}, title = {On the possibility of electromagnetically induced transparency in a plasma. I. Infinite plasma}, journal = {Phys. Plasmas}, year = {2000}, volume = {7}, pages = {3145-3155}, abstract = {The theory of electromagnetically induced transparency (EIT) in a plasma [S. E. Harris, Phys. Rev. Lett. 77, 5357 (1996)] is examined in the context of an infinite system. A new dispersion relation is derived which accounts for relativistic effects in an overdense plasma. Several branches of the dispersion relation are plotted and discussed. Particle simulations are used to confirm the findings. (C) 2000 American Institute of Physics. [S1070-664X(00)00407-9]. } } @ARTICLE{GordonMJ00, author = {Gordon, D. F. and Mori, W. B. and Joshi, C.}, title = {On the possibility of electromagnetically induced transparency in a plasma. II. Bounded plasma}, journal = {Phys. Plasmas}, year = {2000}, volume = {7}, pages = {3156-3166}, abstract = {The theory of electromagnetically induced transparency (EIT) in a plasma [S. E. Harris, Phys. Rev. Lett. 77, 5357 (1996)] is examined in the context of a bounded system. It is found via particle simulations that an overdense plasma slab reflects short pulses even in the presence of an EIT passband. However, a two-frequency laser, or "beatwave," will cascade into a Stokes satellite with a frequency below the cut-off frequency. This can lead to an apparent EIT signature if a specific set of parameters are chosen. (C) 2000 American Institute of Physics. [S1070-664X(00)00507-3]. } } @ARTICLE{FleischhauerMS00, author = {Fleischhauer, M. and Matsko, A. B. and Scully, M. O.}, title = {Quantum limit of optical magnetometry in the presence of ac Stark shifts}, journal = {Phys. Rev. A}, year = {2000}, volume = {6201}, pages = {013808}, abstract = {We analyze systematic (classical) and fundamental (quantum) limitations of the sensitivity of optical magnetometers resulting from ac Stark shifts. We show that in contrast to absorption-based techniques, the signal reduction associated with classical broadening can be compensated in magnetometers based on phase measurements using electromagnetically induced transparency (EIT). However due to ac Stark-associated quantum noise the signal-to-noise ratio of FIT-based magnetometers attains a maximum value at a certain laser intensity. This value is independent on the quantum statistics of the light and defines a standard quantum limit of sensitivity. We demonstrate that an EIT-based optical magnetometer in Faraday configuration is the best candidate to achieve the highest sensitivity of magnetic-field detection and give a detailed analysis of such a device. } } @ARTICLE{KozlovE00, author = {Kozlov, V. V. and Eberly, J. H.}, title = {Ultrashort pulses in phaseonium: the interplay between SIT and EIT}, journal = {Opt. Commun.}, year = {2000}, volume = {179}, pages = {85-96}, abstract = {Pulse propagation in the pure-state three-level medium called phaseonium by Marlan Scully is studied both analytically and numerically. Distinctions between SIT-type pulses (e.g., simultons) and EIT-type pulses are most naturally revealed by making use of dark and bright dressed-state amplitudes. We show that EIT-type and SIT-type pulses propagating in phaseonium are to be distinguished by the type of population evolution that they induce. (C) 2000 Elsevier Science B.V. All rights reserved. } } @ARTICLE{DormanKM00, author = {Dorman, C. and Kucukkara, I. and Marangos, J. P.}, title = {Density dependent effects due to residual susceptibilities in a four-wave mixing scheme with electromagnetically induced transparency}, journal = {Opt. Commun.}, year = {2000}, volume = {180}, pages = {263-270}, abstract = {We have studied the generation of vacuum ultraviolet radiation (at 123.6 nm) produced in a resonant four-wave-mixing scheme in krypton, enhanced by electromagnetically induced transparency. The interplay between the non-linear susceptibility (governing the wave-mixing), the linear susceptibility (governing the absorption and dispersion), and the density-length product was examined both experimentally and numerically. We observe favourable scaling of the yield with density-length product (NL) up to a value of 5 X 10(16) cm(-2). Above this NL value the yield decreases due to the background wave-vector mismatch (Delta k(resid)), which arises from the additional atomic energy levels outside the three considered in the EIT enhanced mixing scheme. Our results suggest that further enhancements in frequency up-conversion can be achieved by employing a buffer gas as a phase matching agent. (C) 2000 Elsevier Science B.V. All rights reserved. } } @ARTICLE{SchmidtR00, author = {Schmidt, H. and Ram, R. J.}, title = {All-optical wavelength converter and switch based on electromagnetically induced transparency}, journal = {Appl. Phys. Lett.}, year = {2000}, volume = {76}, pages = {3173-3175}, abstract = {We propose a method for all-optical switching and wavelength conversion using electromagnetically induced transparency (EIT). We discuss the mechanism for the transfer of information in this scheme and determine the conditions for which NxN wavelength conversion can be realized. We compare the properties and limits of an EIT-based switch to conventional wavelength converters. (C) 2000 American Institute of Physics. [S0003-6951(00)03022-9]. } } @ARTICLE{ChenLY00, author = {Chen, Y. C. and Lin, C. W. and Yu, I. A.}, title = {Role of degenerate Zeeman levels in electromagnetically induced transparency}, journal = {Phys. Rev. A}, year = {2000}, volume = {6105}, pages = {053805}, abstract = {We have observed various Lambda-type electromagnetically induced transparency (EIT) spectra in laser-cooled Rb-87 atoms of different laser polarization configurations. Unexpected profiles occur in the EIT spectra. We have found the degenerate Zeeman sublevels are responsible for these profiles. The experimental data are in good agreement with the results from the theoretical calculation which takes into account all the 13 Zeeman levels in the Lambda system. Our study demonstrates that Zeeman sublevels play important roles in quantum interference phenomena such as EIT and amplification without population inversion (AWI), and should be taken into account in the analysis of these phenomena. } } @ARTICLE{EntinRBB00, author = {Entin, V. M. and Ryabtsev, I. I. and Boguslavskii, A. E. and Beterov, I. M.}, title = {Experimental implementation of a four-level N-type scheme for the observation of electromagnetically induced transparency}, journal = {Jetp Lett.}, year = {2000}, volume = {71}, pages = {175-177}, abstract = {A nondegenerate four-level N-type scheme was experimentally implemented to observe electromagnetically induced transparency (EIT) at the Rb-87 D-2 line. Radiations of two independent external-cavity semiconductor lasers were used in the experiment, the current of one of them being modulated at a frequency equal to the hyperfine-splitting frequency of the excited 5P(3/2) level. In this case, apart from the main EIT dip corresponding to the two-photon Raman resonance in a threelevel Lambda-scheme, additional dips detuned from the main dip by a frequency equal to the frequency of the HF generator were observed in the absorption spectrum. These dips were due to an increase in the medium transparency at frequencies corresponding to the three-photon Raman resonances in four- level N-type schemes. The resonance shapes are analyzed as functions of generator frequency and magnetic field. (C) 2000 MAIK "Nauka/Interperiodica". } } @ARTICLE{PodshivalovMOSW99, author = {Podshivalov, A. A. and Matveev, O. I. and Omenetto, N. and Smith, B. W. and Winefordner, J. D.}, title = {Laser-induced population depletion effects in double resonance excitation with Hg-202 vapors}, journal = {Spectroc. Acta Pt. B-Atom. Spectr.}, year = {1999}, volume = {54}, pages = {2157-2165}, abstract = {By monitoring the green fluorescence transition of mercury vapor 7 S-3(1) --> 6 P-3(2)0 (546.074 nm) excited by two pulsed dye lasers tuned at two connected atomic resonant frequencies, i.e. 6 S-1(0) --> 6 P-3(1)0 (253.652 nm) and 6 P-3(1)0 --> 7 S3(1) (435.835 nm), a decrease in the green fluorescence yield is experimentally observed when the intensity of the 435.835-nm excitation transition exceeds similar to 5 kW/cm(2). A similar result is obtained at the yellow fluorescence transition 6 D- 3(1) --> 6 P-1(1)0 (578.967 nm) when the second step is tuned to the 6 P-3(1)0 --> 6 D-3(1) transition (313.159 nm). At the same time, an increase in the transmittance of the ground state transition (253.652 nm) is observed. It is speculated that this effect, which occurs only when both laser pulses are temporally coincident, and is therefore not due to photoionization, can be ascribed to the existence of laser induced effects, such as a.c. Stark splitting of levels and possibly electromagnetically-induced transparency (EIT). Our experiment does not allow us to distinguish between these two effects, nor their quantitative evaluation, However, it is stressed that one cannot overlook them in those atomic multi-step excitation experiments in low collisional environments where a depletion of an intermediate level is involved, as for example in the case of atomic fluorescence: dip spectroscopy or atomic multistep and multiphoton resonance ionization spectroscopy. (C) 1999 Published by Elsevier Science B.V. All rights reserved. } } @ARTICLE{BentleyLL00, author = {Bentley, C. L. and Liu, J. R. and Liao, Y.}, title = {Cavity electromagnetically induced transparency of driventhree-level atoms: A transparent window narrowing below a natural width}, journal = {Phys. Rev. A}, year = {2000}, volume = {6102}, pages = {023811}, abstract = {Steady-state dynamics of a Lambda atom in a ring cavity driven by two coherent fields are studied for arbitrary detunings, arbitrary incoherent pumping, and coherent driving intensities. Effects of both cavity and effective atom number on electromagnetically induced transparency (EIT) are pointed out. New physical pictures for cavity EIT are given in terms of collective cooperative coefficients and dispersion experienced by the probe. In the regime of smaller collective cooperative coefficients, an absorption-gain profile is reduced to that of a general EIT estimated by the imaginary part of a corresponding dipole moment, and its transparency window is directly proportional to power broadening, if the total Rabi frequency is large enough. But in the region of larger collective cooperative coefficients which means a dense atomic medium, longer optical path, or high-Q cavity, EIT is determined not only by the imaginary part but also by the real part of the corresponding dipole moment, which results in the possibility of observing an EIT central peak with a subnatural width, while there may be nearly no power broadening.} } @ARTICLE{WernerI00, author = {Werner, M. J. and Imamoglu, A.}, title = {Photon-photon interactions in cavity electromagnetically induced transparency}, journal = {Phys. Rev. A}, year = {2000}, volume = {6001}, pages = {011801}, abstract = {Dissipation-free photon-photon interaction at the single-photon level is studied in the context of cavity electromagnetically induced transparency (EIT). For a single multilevel atom exhibiting EIT in the strong cavity-coupling regime, the anharmonicity of the atom-cavity system has an upper bound determined by single atom-photon coupling strength. A photon blockade effect is inferred to occur for both singleand multiatom cases from the behavior of transition rates between dressed states of the system. Numerical calculations of the second-order coherence function indicate that photon antibunching in both single- and two-atom cases are strong and comparable. } } @ARTICLE{DongG00, author = {Dong, P. and Gao, J. Y.}, title = {Appearance and disappearance of hole-burning behind an electromagnetically induced transparency window}, journal = {Phys. Lett. A}, year = {2000}, volume = {265}, pages = {52-57}, abstract = {We propose a new scheme of hole-burning when a strong coherent field, which makes an Electromagnetically Induced Transparency (EIT) window, could make more or disappearance of hole-burning in a Doppler broadening medium under different conditions. (C) 2000 Published by Elsevier Science B.V. ALI rights reserved.} } @ARTICLE{BentleyL99, author = {Bentley, C. L. and Liu, J. R.}, title = {LWI in a driven Lambda three-level atom and effects of the probe laser on EIT}, journal = {Opt. Commun.}, year = {1999}, volume = {169}, pages = {289-299}, abstract = {Steady-state dynamics of a Lambda atom driven by two coherent fields is studied for arbitrary detunings, arbitrary incoherent pumping and coherent driving intensities. Effects of a strong probe on EIT are worked out. Features of EFT and LWI are presented in a new physical picture on the basis of the concepts of quantum interference and coherence. In the weak field regime, an absorption-gain profile is the subtraction of two Lorentzians with the same central frequency but different widths and heights. This case is mostly the result of quantum interference and coherence rather than the result of AutlerTownes level splitting. In a strong field regime, however, the profile is the addition of two Lorentzian-like components with different central frequencies but the same width, where Autler- Townes splitting and quantum interference are equally important. (C) 1999 Published by Elsevier Science B.V. All rights reserved. } } @ARTICLE{WeiM99, author = {Wei, C. J. and Manson, N. B.}, title = {Observation of the dynamic Stark effect on electromagnetically induced transparency}, journal = {Phys. Rev. A}, year = {1999}, volume = {60}, pages = {2540-2546}, abstract = {Using electron-spin-resonance transitions within the nitrogenvacancy center in diamond, we have obtained a sharp electromagnetically induced transparency (EIT) feature when the coupling and probing fields satisfy a two-photon resonance condition. In this paper it is shown that by the application of an additional driving field the sharp EIT feature can be split into a doublet or a triplet depending on the experimental configuration. The results are interpreted in terms of dynamic Stark splitting of the EIT feature, and the spectra are shown to be related to Autler-Townes and Mellow spectra. [S1050- 2947(99)10209-9]. } } @ARTICLE{MoonKKK99, author = {Moon, H. S. and Kim, H. A. and Kim, B. S. and Kim, J. B.}, title = {Electromagnetically induced transparency in an ideal threelevel system in Rb-87 atoms}, journal = {J. Korean Phys. Soc.}, year = {1999}, volume = {35}, pages = {207-211}, abstract = {We have suggested an ideal three-level system, which is the transition between the magnetic F = 1 and F' = 1 sublevels in the Rb-87 atom, for studying atomic coherence, and we have studied the electromagnetically induced transparency(EIT) in that system. With two counter-rotating circularly polarized lasers, Doppler-free absorption reduction in an ideal R-type three-level atomic system is observed up to 95 \%, including optical pumping. After adding an incoherent repumping beam from F = 2 to F = 1 through F' = 2, the maximum absorption reduction is approximately the same as 95 \%. In a magnetic field, EIT shows dispersion-like spectrum because of the detuning effect of the coupling laser due to Zeeman splitting of the magnetic sublevels. } } @ARTICLE{WeiM99, author = {Wei, C. J. and Manson, N. B.}, title = {Observation of electromagnetically induced transparency within an electron spin resonance transition}, journal = {J. Opt. B-Quantum Semicl. Opt.}, year = {1999}, volume = {1}, pages = {464-468}, abstract = {A sharp transparency feature is induced in an allowed electron spin resonance (ESR) transition by driving a nominally spinforbidden transition. The width of the feature is narrower than the homogeneous linewidth of the ESR transition and is interpreted as being associated with electromagnetically induced transparency (EIT). Measurements are made for the nitrogen-vacancy centre in diamond and the signals are detected using a coherent optical technique. } } @ARTICLE{HamHKS99, author = {Ham, B. S. and Hemmer, P. R. and Kim, M. K. and Shahriar, S. M.}, title = {Quantum interference and its potential applications in a spectral hole-burning solid}, journal = {Laser Phys.}, year = {1999}, volume = {9}, pages = {788-796}, abstract = {We have reviewed observations of electromagnetically induced transparency (EIT) in solids and its potential applications such as enhanced four-wave mixing, Raman excited optical memory, and rf-coupled optical gain. } } @ARTICLE{SchmidtNCMGI99, author = {Schmidt, H. and Nikonov, D. E. and Campman, K. L. and Maranowski, K. D. and Gossard, A. C. and Imamoglu, A.}, title = {Quantum interference in semiconductor quantum wells}, journal = {Laser Phys.}, year = {1999}, volume = {9}, pages = {797-812}, abstract = {We present a review of theoretical and experimental evidence for quantum interference in intersubband transitions of coupled semiconductor quantum wells. Intersubband absorption spectra are calculated using semiconductor Bloch equations to include the Coulomb interaction between the conduction band electrons. We demonstrate that the absorption spectra must be viewed as collective excitations. In a configuration analogous to electromagnetically induced transparency (EIT) in atomic systems, we show that quantum interference occurs between the levels of these collective intersubband excitations rather than single electronic states. Experiments which demonstrate quantum interference in coupled quantum wells due to tunneling induced transparency (TIT) are presented. The design issues for such samples are reviewed, and the effects of monolayer growth fluctuations on the spectra are simulated. Finally, we discuss the temperature dependence of TIT and demonstrate that the quantum interference persists at room temperature. } } @ARTICLE{BoonZMD99, author = {Boon, J. R. and Zekou, E. and McGloin, D. and Dunn, M. H.}, title = {Comparison of wavelength dependence in cascade-, Lambda-, and Vee-type schemes for electromagnetically induced transparency}, journal = {Phys. Rev. A}, year = {1999}, volume = {59}, pages = {4675-4684}, abstract = {We present a theoretical study of the effects of mismatching wavelengths for the coupling and probe fields in Dopplerbroadened media for the three basic energy level configurations commonly used to realize electromagnetically induced transparency (EIT). Three wavelength regimes are considered: mismatched wavelengths for which the coupling frequency is greater than the probe frequency, matched wavelengths for which the coupling and probe frequencies are equal, and mismatched wavelengths for which the probe frequency is greater than the coupling frequency. The transparency that may be induced in these regimes is compared for the cascade-, Lambda-, and Vee- type systems. We show that in the first mismatched regime (lambda(c) < lambda(p)) EIT is possible in all schemes and is in fact stronger than in the matched case. It is also demonstrated that for the second mismatched regime (lambda(c) > lambda(p)) EIT can be realized most readily in the Vee-type configuration in the presence of Doppler broadening. These predictions are explained by considering the absorption as a function of both the probe field detuning and the atomic velocity. [S1050-2947(99)01006-9]. } } @ARTICLE{MitsunagaI99, author = {Mitsunaga, M. and Imoto, N.}, title = {Observation of an electromagnetically induced grating in cold sodium atoms}, journal = {Phys. Rev. A}, year = {1999}, volume = {59}, pages = {4773-4776}, abstract = {We have observed diffraction signals by a grating originating from electromagnetically induced transparency (EIT) in a threelevel Lambda system of cold sodium atoms. Theoretical and experimental analyses of this phenomenon, called the electromagnetically induced grating (EIG), have revealed that EIG spectra exhibit background-free, Lorentzian signal profiles regardless of the pump frequencies, making a clear contrast to the case of ordinary EIT spectra. } } @ARTICLE{SadeghiM99, author = {Sadeghi, S. M. and Meyer, J.}, title = {Two-field electromagnetically induced transparency and switching between ultranarrow absorption and gain features in rubidium atoms}, journal = {Phys. Rev. A}, year = {1999}, volume = {59}, pages = {3998-4004}, abstract = {We study the generation of an ultranarrow gain spectrum in an atomic transition when the upper transition level is coupled to the lower transition level by one laser and to a metastable state by another laser. It is shown that this spectrum switches abruptly into an ultranarrow absorption line with an increase in the first laser intensity. These results are explained by investigating the electromagnetically induced transparency (EIT) in a system where the upper transition level is coupled to two metastable states by two laser fields (ir; system). We discuss various features of such a transparency and show how it can be described as a structuring process, similar to the laser-induced continuum structure. Utilizing such a description of EIT, we explain the ultranarrow gain generation as a stimulated Rayleigh scattering process. [S1050-2947(99)048052]. } } @ARTICLE{HamSH99, author = {Ham, B. S. and Shahriar, S. M. and Hemmer, P. R.}, title = {Electromagnetically induced transparency over spectral holeburning temperature in a rare-earth-doped solid}, journal = {J. Opt. Soc. Am. B-Opt. Phys.}, year = {1999}, volume = {16}, pages = {801-804}, abstract = {We have observed electromagnetically induced transparency (EIT) in rare-earth Pr3+-doped Y2SiO5 over the spectral hole-burning temperature. The transmission of the probe laser beam is increased by a factor of exp(1.4) at 12 K when a coupling laser of 1.2 kW/cm(2) is applied to the system. The observation of EIT over the spectral hole-burning temperature in a rare-earthdoped solid represents important progress toward high-density echo-based optical memories at higher temperatures. (C) 1999 Optical Society of America [S0740-3224(99)01605-7]. } } @ARTICLE{Kofman99, author = {Kofman, A. G.}, title = {Intensity-fluctuation-induced spectral structure}, journal = {Europhys. Lett.}, year = {1999}, volume = {46}, pages = {164-170}, abstract = {Electromagnetically induced transparency (EIT) with chaotic field is considered for the constructive-interference case (i.e.,when the material transition is much narrower than the coupled one). The field intensity fluctuations are shown to induce a narrow peak at the material frequency in addition to the familiar Antler-Towns doublet. The dependence of the fluctuation-induced peak on the field bandwidth nu is obtained analytically and numerically. EIT is shown to increase with nu for sufficiently small nu. } } @ARTICLE{TokarykZS99, author = {Tokaryk, D. W. and Zhang, G. Z. and Stoicheff, B. P.}, title = {Nonlinear optical generation in a hydrogen discharge}, journal = {Phys. Rev. A}, year = {1999}, volume = {59}, pages = {3116-3119}, abstract = {Sum-frequency generation with electromagnetically induced transparency (EIT) has been examined in a hydrogen discharge. EIT is demonstrated in the 3p-1s and 4p-1s transitions at 102.6 and 97.3 nln, respectively, with increased efficiency of generation arising from higher H-atom density, although competing effects due to the presence of Hz distort the line shapes of these spectra. Only for shorter-wavelength transitions (such as 7p-1s and 8p-1s) that show very large shifts and distortions is there a decrease in intensity in comparison with generated radiation from H atoms external to the discharge. [S1050-2917(99)01404-3]. } } @ARTICLE{KorsunskyLHBW99, author = {Korsunsky, E. A. and Leinfellner, N. and Huss, A. and Baluschev, S. and Windholz, L.}, title = {Phase-dependent electromagnetically induced transparency}, journal = {Phys. Rev. A}, year = {1999}, volume = {59}, pages = {2302-2305}, abstract = {We report on the experimental demonstration of phase-dependent electromagnetically induced transparency (EIT). This effect is based on a quantum interference in closed-loop schemes of interaction of atoms with the radiation. It allows us to control optical properties of the medium by the phases of the laser fields. We discuss some of the possible applications of phase-dependent EIT. [S1050-2947(99)01003-3]. } } @ARTICLE{Fleischhauer99, author = {Fleischhauer, M.}, title = {Electromagnetically induced transparency and coherent-state preparation in optically thick media}, journal = {Opt. Express}, year = {1999}, volume = {4}, pages = {107-112}, abstract = {The preparation of an optically dense ensemble of three-level systems in dark states of the interaction with coherent radiation is discussed. It is shown that methods involving spontaneous emissions of photons such as Raman optical pumping fail to work beyond a critical density due to multiple scattering and trapping of these photons and the associated decay of the dark state(s). In optically thick media coherentstate preparation is only possible by entirely coherent means such as stimulated Raman adiabatic passage (STIRAP). It is shown that STIRAP is the underlying physical mechanism for electromagnetically induced transparency (EIT). (C) 1998 Optical Society of America. } } @ARTICLE{IchimuraYG98, author = {Ichimura, K. and Yamamoto, K. and Gemma, N.}, title = {Evidence for electromagnetically induced transparency in a solid medium}, journal = {Phys. Rev. A}, year = {1998}, volume = {58}, pages = {4116-4120}, abstract = {Strong evidence indicating the occurrence of electromagnetically induced transparency (EIT) in a solid medium was found. Fluorescence reduction due to Err was observed in solids. The excitation intensity dependence of the fluorescence reduction was found to be consistent with theoretical predictions for EIT. It was experimentally demonstrated that the essential condition for the observation of EIT in solids is that the Rabi frequency of excitation must be larger than the inhomogeneous width of the transition between the two states coupled to the third state by the pair of optical fields. [S1050-2947(98)00311-9]. } } @ARTICLE{DormanM98, author = {Dorman, C. and Marangos, J. P.}, title = {Resonant sum-difference frequency mixing enhanced by electromagnetically induced transparency in krypton}, journal = {Phys. Rev. A}, year = {1998}, volume = {58}, pages = {4121-4132}, abstract = {We report experiments that investigate the generation of coherent VUV radiation at 123.6 nm via a resonant sum- difference frequency mixing scheme in Kr. One of the mixing fields at 212.55 nm was in two-photon resonance with the transition between the 4p(6) S-1 ground state and the 4p(5) 5p[0,1/2] excited state (94 093.7 cm(-1)). The second field (the coupling field) at 759 nm was in single-photon resonance with the transition between the 4p(5) 5p[0,1/2] state and the 4p(5) 5s[1,1/2] state at 80 917.6 cm(-1). The presence of the coupling field leads to electromagnetically induced transparency (EIT) at the wavelength of the generated field, 123.6 nm. This is predicted to enhance the four-wave-mixing efficiency by a large factor. We have studied the dependence of the four-wave mixing process on the detuning and strength of the coupling field. The efficiency for four-wave mixing was found to be enhanced by a significant factor (>5) by the EIT effect when the resonant coupling field strength exceeded about half the Doppler width (0.1 cm(-1)). A calculation for monochromatic fields and a uniform slab of gas provided qualitative agreement with the results of experiment. The relative conversion efficiency for this resonant mixing scheme is found to be 10(4) times greater than that for a similar scheme where the coupling laser is tuned far (1270 cm(-1)) off resonance. A substantial part of this resonant enhancement can thus be attributed to the EIT effect. [S1050-2947(98)00511-3].} } @ARTICLE{YamamotoIG98, author = {Yamamoto, K. and Ichimura, K. and Gemma, N.}, title = {Enhanced and reduced absorptions via quantum interference: Solid system driven by a rf field}, journal = {Phys. Rev. A}, year = {1998}, volume = {58}, pages = {2460-2466}, abstract = {We observed quantum interference effects in steady-state optical absorption in a V-type three-level system of Pr3+:YAlO3 where a hyperfine transition between two upper levels was homogeneously broadened by pure dephasing. This V-type system was excited by a single driving radio-frequency (rf) field and two probe laser fields (quantum-beat scheme). The probe absorption was constructively or destructively affected by the phase of the driving rf field. In contrast, under two-laser excitation without application of the rf, no absorption change due to electromagnetically induced transparency (EIT) was observed. A comparison of observations and theoretical predictions revealed that the quantum-beat scheme generates quantum interference even when the dephasing rate between the two upper levels is comparable with the Rabi frequency of the probe laser, and completely destroys EIT. } } @ARTICLE{ChenDMV98, author = {Chen, H. X. and Durrant, A. V. and Marangos, J. P. and Vaccaro, J. A.}, title = {Observation of transient electromagnetically induced transparency in a rubidium Lambda system}, journal = {Phys. Rev. A}, year = {1998}, volume = {58}, pages = {1545-1548}, abstract = {Observation of transient effects in electromagnetically induced transparency (EIT) is reported in Rb-85 cooled in a magnetooptical trap. The transmission of a weak probe beam in resonance with the 5S(1/2)(F=3) to 5P(3/2)(F=3) hyperfine transition increased transiently when a relatively strong coupling field in resonance with the 5S(1/2)(F=2) to 5P(3/2)(F=3) hyperfine transition was switched on rapidly using a Pockels cell. The probe transient showed an initial Rabi half-cycle overshoot before settling down to steady-state EIT. The results agreed well with computations using a three-state model of the Lambda system. The computations also suggest that transient gain should be observed with coupling field power only four times larger than that presently available to us. [S1050-2947(98)03308-3]. } } @ARTICLE{SchmidtI98, author = {Schmidt, H. and Imamoglu, A.}, title = {High-speed properties of a phase-modulation scheme based on electromagnetically induced transparency}, journal = {Opt. Lett.}, year = {1998}, volume = {23}, pages = {1007-1009}, abstract = {Recently a cross-phase modulation scheme that yields giant Kerr nonlinearities by use of an electromagnetically induced transparency (EIT) was proposed [Schmidt and Imamoglu, Opt. Lett. 21, 1936 (1996)]. We analyze the high-speed properties of this scheme for short-pulse propagation. the high-speed properties of this scheme for short-pulse propagation. system and show that for short pulses one-photon losses are dominant. We demonstrate that over the entire width the attainable phase shift in an EIT scheme with a quasi-cm coupling field is orders of magnitude higher than in a conventional three-level scheme or in EIT schemes, in which matched pulses are used to create the transparency. (C) 1998 Optical Society of America.} } @ARTICLE{LeeS98, author = {Lee, H. and Scully, M. O.}, title = {The physics of EIT and LWI in V-type configurations}, journal = {Found. Phys.}, year = {1998}, volume = {28}, pages = {585-600}, abstract = {We review the concepts and the physics behind electromagnetically induced transparency (EIT) and lasing without inversion (LWI) for various models of the V-type configurations. } } @ARTICLE{BaluschevLKW98, author = {Baluschev, S. and Leinfellner, N. and Korsunsky, E. A. and Windholz, L.}, title = {Electromagnetically induced transparency in a sodium vapour cell}, journal = {Eur. Phys. J. D}, year = {1998}, volume = {2}, pages = {5-10}, abstract = {The report on an investigation of electromagnetically induced transparency (EIT) in sodium vapour. In our experiment, sodium atoms are excited on the D-1-line with laser radiation containing two components with a frequency difference close to that of the two hyperfine ground states of sodium (1.772 GHz). Such an excitation leads to coherent trapping of atomic population in "dark" superpositional states, which dramatically reduces the absorption of light. A frequency transparency window is measured to have a subnatural width, which is a clear indication of coherent population trapping. Dependence of EIT on laser frequencies and intensities, on the magnetic field strength as well as on the temperature of the sodium vapour is studied. } } @ARTICLE{DormanMP98, author = {Dorman, C. and Marangos, J. P. and Petch, J. C.}, title = {Investigation of vacuum ultraviolet generation in a resonant four-wave mixing scheme in krypton with electromagnetically induced transparency}, journal = {J. Mod. Opt.}, year = {1998}, volume = {45}, pages = {1123-1135}, abstract = {We report experiments investigating a resonant sum-difference frequency mixing scheme in krypton producing coherent radiation at 123.6 nm (i.e. in the vacuum ultraviolet (VUV)). Owing to the resonant nature of this scheme, electromagnetically induced transparency (EIT) plays a crucial role in the generation of this coherent radiation, resulting in a greatly enhanced conversion efficiency. This is the first time a resonant sumdifference mixing scheme involving EIT, that generates VUV radiation, has been investigated experimentally. Our results are in broad agreement with theoretical predictions. Measurements are presented of the dependence of VUV generation on laser detuning (in the range +/-3 cm(-1)) and laser powers. In particular the dependence on the coupling field strength has been studied in the range of coupling held Rabi frequencies Omega(c) = 0.05-3 cm(-1). We estimate an enhancement in the conversion efficiency, compared with the non-resonant case, of greater than 10(2). } } @ARTICLE{CroninWLF98, author = {Cronin, A. D. and Warrington, R. B. and Lamoreaux, S. K. and Fortson, E. N.}, title = {Studies of electromagnetically induced transparency in thallium vapor and possible utility for measuring atomic parity nonconservation}, journal = {Phys. Rev. Lett.}, year = {1998}, volume = {80}, pages = {3719-3722}, abstract = {Motivated by the potential use of electromagnetically induced transparency (EIT) to measure atomic parity nonconservation (PNC), we have studied EIT and associated optical rotation for a three-level system in thallium vapor. EIT allows sub-Doppler resolution of the 6P(1/2) --> 6P(3/2) mixed magnetic dipole, electric quadrupole transition at 1.28 mu m when 0.535-mu m radiation acts on the 6P(3/2) --> 7S(1/2) transition. Our measurements include rotation due to electromagnetically induced birefringence and Faraday rotation perturbed by EIT. We also identify a new method for determining the amplitude ratio E2/M1 for the 1.28-mu m transition. The possible advantages of an EIT technique for measuring atomic PNC are discussed in the context of our results. } } @ARTICLE{KuhnSB98, author = {Kuhn, A. and Steuerwald, S. and Bergmann, K.}, title = {Coherent population transfer in NO with pulsed lasers: the consequences of hyperfine structure, Doppler broadening and electromagnetically induced absorption}, journal = {Eur. Phys. J. D}, year = {1998}, volume = {1}, pages = {57-70}, abstract = {Coherent population transfer between vibrational levels of the NO molecule induced by the interaction of two delayed laser pulses, also referred to as stimulated Raman scattering involving adiabatic passage (STIRAP), is studied experimentally in a molecular beam and in the bulk. The consequences of hyperfine splitting and Doppler broadening are discussed in detail. Unlike in previous studies of this kind, transfer occurs simultaneously between more than one group of non degenerate levels. In a molecular beam or in the bulk, the transfer efficiency of STIRAP exceeds that, obtained by Stimulated Emission Pumping (SEP) by a factor of 3.6 or 15, respectively. We estimate the absolute transfer efficiency T in the beam to be T approximate to 60\%, while T approximate to 18\% is found in the bulk. In both cases: this is 60\% of the maximum value expected from numerical studies. Possible reasons for this discrepancy are discussed. Finally we show that the absorption of a pump pulse in a weakly absorbing medium is significantly enhanced by the presence of a copropagating Stokes pulse when the Rabi frequency Omega s of the latter is smaller than the width of the Doppler profile Delta nu(D). The relation of this observation to the phenomenon of Electromagnetically Induced Transparency (EIT), which is observed for Omega s >> Delta nu(D), is also discussed.} } @ARTICLE{Marangos98, author = {Marangos, J. P.}, title = {Topical review electromagnetically induced transparency}, journal = {J. Mod. Opt.}, year = {1998}, volume = {45}, pages = {471-503}, abstract = {The subject of electromagnetically induced transparency (EIT) is reviewed in this paper. Emphasis is placed on the experimental work reported in this field since 1990. Theoretical work is also covered, although it is not intended to review all the very numerous recent theoretical treatments on this topic. The basic physical ideas behind EIT are elucidated. The relation of EIT to other processes involving laser-induced atomic coherence, such as coherent population trapping, coherent adiabatic population transfer and lasing without inversion, is discussed. Experimental work is described covering the following topics: EIT with pulsed and continuouswave sources, lasing without inversion, pulse propagation in a laser dressed medium and EIT in nonlinear optical processes. A full set of references and a bibliography are included.} } @ARTICLE{LukinFSV98, author = {Lukin, M. D. and Fleischhauer, M. and Scully, M. O. and Velichansky, V. L.}, title = {Intracavity electromagnetically induced transparency}, journal = {Opt. Lett.}, year = {1998}, volume = {23}, pages = {295-297}, abstract = {The effect of intracavity electromagnetically induced transparency (EIT) on the properties of optical resonators and active laser devices is discussed theoretically. Pronounced frequency pulling and cavity-linewidth narrowing are predicted. The EIT effect can be used to reduce classical and quantumphase noise of the beat note of an optical oscillator substantially. Fundamental limits of this stabilization mechanism as well as its potential application to high- resolution spectroscopy are discussed. (C) 1998 Optical Society of America. } } @ARTICLE{VaccaroDRHCH98, author = {Vaccaro, J. A. and Durrant, A. V. and Richards, D. and Hopkins, S. A. and Chen, H. X. and Hill, K. E.}, title = {Stochastic wavefunction diagrams for electromagnetically induced transparency, inversionless gain and shelving}, journal = {J. Mod. Opt.}, year = {1998}, volume = {45}, pages = {315-333}, abstract = {A rigorous diagrammatic description of stochastic wavefunction evolution for electromagnetically induced transparency (EIT) and inversionless gain in coherently driven three-level systems is developed and applied to transient and steady-state conditions. Wavefunction trajectories are illustrated for cases that include Lambda and V-type EIT, shelving and dressed-state resonances. } } @ARTICLE{ScullyBRZ97, author = {Scully, M. O. and Bednar, C. J. and Rostovtsev, Y. and Zhu, S. Y.}, title = {Counter-counter-intuitive quantum coherence effects}, journal = {Philos. Trans. R. Soc. Lond. Ser. A-Math. Phys. Eng. Sci.}, year = {1997}, volume = {355}, pages = {2305-2311}, abstract = {The study of an ensemble of phase-coherent atoms has recently lead to interesting theoretical innovations and experimental demonstrations of counter-intuitive effects such as electromagnetically induced transparency (EIT), lasing without inversion (LWI), enhancement of index of refraction and ultra- large nonlinear susceptibility. In the present notes, we report a couple of new effects along these lines. In fact, it would be fair to call them surprises even in the repertoire of 'counter- intuitive effects', i.e. 'counter-counter-intuitive effects'. Specifically, we will show that the LWI concept, which is based on quantum coherence, has an interesting counterpart in the classical physics of free electron laser operation. In other current work, we find that it is possible to 'lock' atoms in an excited state via atomic coherence. It is, by now, not surprising that such a phase-coherent ensemble can show holes or dark lines in the emission spectrum. It is surprising that we can lock atoms in an excited (normally decaying) state via atomic coherence and interference. Such a phase-coherent collection of atoms, i.e. 'phaseonium', is indeed a novel new state of matter. } } @ARTICLE{HamHS97, author = {Ham, B. S. and Hemmer, P. R. and Shahriar, M. S.}, title = {Efficient electromagnetically induced transparency in a rareearth doped crystal}, journal = {Opt. Commun.}, year = {1997}, volume = {144}, pages = {227-230}, abstract = {We have observed up to 100\% transmission of a probe field at line center due to electromagnetically induced transparency (EIT) in an optically dense rare-earth crystal of Pr3+ doped Y2SiO5 at 5.5 K. We also have examined both laser field intensity and temperature dependence of the EIT. Efficient EIT in this crystal opens potential applications such as efficient high-resolution image processing and signal processing, and optical data storage as well as lasers without population inversion in solids. (C) 1997 Elsevier Science B.V. } } @ARTICLE{CataliottiFPI97, author = {Cataliotti, F. S. and Fort, C. and Prevedelli, M. and Inguscio, M.}, title = {Full resolution of the Autler-Townes Zeeman multiplet for cold cesium atoms in a three-level Lambda-type configuration}, journal = {Can. J. Phys.}, year = {1997}, volume = {75}, pages = {767-773}, abstract = {Cold cesium atoms released from a magneto-optical trap were investigated in Lambda-type configurations of hyperfine levels of the D-2 line. Electromagnetically induced transparency (EIT) was observed and studied as a function of relevant parameters of the pump-probe lasers. Full resolution of the Zeeman degeneracy was obtained for the first time through the different dependence of the Autler-Townes effect. } } @ARTICLE{LukinFZRVHS97, author = {Lukin, M. D. and Fleischhauer, M. and Zibrov, A. S. and Robinson, H. G. and Velichansky, V. L. and Hollberg, L. and Scully, M. O.}, title = {Spectroscopy in dense coherent media: Line narrowing and interference effects}, journal = {Phys. Rev. Lett.}, year = {1997}, volume = {79}, pages = {2959-2962}, abstract = {Spectroscopic properties of coherently prepared, optically dense atomic media are studied experimentally and analyzed theoretically. It is shown that in such media the power broadening of the resonances can be substantially reduced. A density-dependent spectral narrowing of the electromagnetically induced transparency (EIT) window and novel, even narrower, resonances superimposed on the EIT line are observed in dense Rb vapor. A nonlinear two-photon spectroscopic technique based on coherent atomic media and combining high resolution with a large signal-to-noise ratio seems feasible. } } @ARTICLE{Kofman97, author = {Kofman, A. G.}, title = {Electromagnetically induced transparency with coherent and stochastic fields}, journal = {Phys. Rev. A}, year = {1997}, volume = {56}, pages = {2280-2291}, abstract = {This paper deals with electromagnetically induced transparency (EIT), i.e., a significant suppression of absorption at a material transition (in the form of a dip in an absorption spectrum), due to a strong laser field, coupling the excited level with an auxiliary excited (unpopulated) level. A comprehensive theory of EIT is developed for the cases of coherent and Markovian phase-and amplitude-phase-fluctuating coupling fields. For a coherent coupling field, a shift of the absorption minimum from the two-photon resonance is revealed in the off-resonance case. Two models of amplitude-phase fluctuating fields are considered: the chaotic field and the uncorrelated-jump field. Closed analytical expressions for EIT line shape are derived and exact Limits of different regimes of EIT an obtained, the emphasis being on the near-resonance case, The main conclusion is that an amplitude-phase-fluctuating field can induce significant transparency, though reduced in comparison to a phase-fluctuating field of the same average intensity and bandwidth. EIT decreases with the increase of the bandwidth for all stochastic models considered. EIT with a chaotic field is generally less pronounced than EIT with an uncorrelated-jump field of the same intensity and bandwidth, the difference increasing with the field intensity. The possibility of experimental verification of the results obtained is discussed. } } @ARTICLE{HamSH97, author = {Ham, B. S. and Shahriar, M. S. and Hemmer, P. R.}, title = {Enhanced nondegenerate four-wave mixing owing to electromagnetically induced transparency in a spectral holeburning crystal}, journal = {Opt. Lett.}, year = {1997}, volume = {22}, pages = {1138-1140}, abstract = {We have demonstrated electromagnetically induced transparency (EIT) in an inhomogeneously broadened spectral hole-burning system of Pr3+-doped Y2SiO5 at 6 K. We have also shown enhancement of four-wave mixing under conditions of reduced absorption. This demonstration opens the possibilities of pursuing EIT applications such as high-resolution optical image processing and optical data storage in solids. (C) 1997 Optical Society of America. } } @ARTICLE{ZhangTSH97, author = {Zhang, G. Z. and Tokaryk, D. W. and Stoicheff, B. P. and Hakuta, K.}, title = {Nonlinear generation of extreme-ultraviolet radiation in atomic hydrogen using electromagnetically induced transparency}, journal = {Phys. Rev. A}, year = {1997}, volume = {56}, pages = {813-819}, abstract = {Sum-frequency generation enhanced by electromagnetically induced transparency (EIT) has been extended to the production of extreme ultraviolet (XUV) radiation in the range 97.3-92.6 nm from np-ls transitions (n = 4-8) in atomic hydrogen. Pulsed radiation Was generated by strong coupling of the np and 2s levels with laser radiation at Balmer wavelengths, and simultaneously (weaker) coupling of the 2s and Is levels by two-photon resonance with 243-nm laser radiation. Investigations were carried out over a range of laser intensities and products of interaction length and atomic density (NL). As the product NL increased, the XUV intensities were greatly enhanced by EIT, and at high NL values, the spectral distributions of some of the generated signals were found to be distorted by the presence of molecular hydrogen. Calculated profiles, modified to incorporate the effects of nearby molecular resonances, were shown to be in good agreement with the observed spectra. } } @ARTICLE{SchmidtCGI97, author = {Schmidt, H. and Campman, K. L. and Gossard, A. C. and Imamoglu, A.}, title = {Tunneling induced transparency: Fano interference in intersubband transitions}, journal = {Appl. Phys. Lett.}, year = {1997}, volume = {70}, pages = {3455-3457}, abstract = {We report the observation of tunneling induced transparency in asymmetric double quantum well structures. Resonant tunneling through a thin barrier is used to coherently couple the two upper states in a three level system of electronic subbands in a GaAs/AlGaAs structure. This creates Fano-type interferences for the collective intersubband excitations in the absorption from the ground state, analogous to electromagnetically induced transparency (EIT) in atomic systems. We observe a 50\% reduction in absorption between the subband resonances which can be explained by taking into account the coherent coupling of the upper states. We analyze the bias dependent absorption spectra and determine the relevant lifetime broadening and dephasing rates for the transitions. (C) 1997 American Institute of Physics. } } @ARTICLE{FortCHIP97, author = {Fort, C. and Cataliotti, F. S. and Hansch, T. W. and Inguscio, M. and Prevedelli, M.}, title = {Gain without inversion on the cesium D-1 line}, journal = {Opt. Commun.}, year = {1997}, volume = {139}, pages = {31-34}, abstract = {We investigated electromagnetically induced transparency (EIT) in a V-type system in cesium at room temperature: a strong coupling laser at 852 nm was locked on the D-2 transition while the transmission of a weak probe at 894 nm has been recorded as the frequency was scanned through the D-1 transition. The addition of an incoherent pump on the D-1 line has allowed for the observation of non-inverted gain. A systematic investigation of the effect for different hyperfine sublevels has been performed as a function of the relevant experimental parameters. } } @ARTICLE{HopkinsUCD97, author = {Hopkins, S. A. and Usadi, E. and Chen, H. X. and Durrant, A. V.}, title = {Electromagnetically induced transparency of laser-cooled rubidium atoms in three-level Lambda-type systems}, journal = {Opt. Commun.}, year = {1997}, volume = {138}, pages = {185-192}, abstract = {We have observed electromagnetically induced transparency (EIT) in laser-cooled rubidium in a magneto-optical trap (MOT). Lambda-type configurations of hyperfine levels of the D2 line were studied, as well as a system utilising degenerate Zeeman sublevels of the ground state. V-type signals were also seen. The perturbing effects of the MOT were found to be small and the results agree well with standard EIT theory for homogeneously-broadened samples. } } @ARTICLE{SandhyaS97, author = {Sandhya, S. N. and Sharma, K. K.}, title = {Atomic coherence effects in four-level systems: Doppler-free absorption within an electromagnetically-induced-transparency window}, journal = {Phys. Rev. A}, year = {1997}, volume = {55}, pages = {2155-2158}, abstract = {We report here an effect in a four-level ladderlike system, which is in contrast to the usual quantum interference effects such as electromagnetically induced transperency (EIT) or coherent population trapping: we predict the occurrence of a narrow absorption peak within the EIT window when an EIT atomic system interacts with an additional driving rf field. The Doppler-free-central absorption appears when the three-photon resonance condition is satisfied. In the limit of the rf field strength Omega(rf)-->0, the usual EIT profile is recovered.} } @ARTICLE{GongXP97, author = {Gong, S. Q. and Xu, Z. Z. and Pan, S. H.}, title = {Electromagnetically induced focusing in a Lambda-type medium}, journal = {Acta Phys. Sin.-Overseas Ed.}, year = {1997}, volume = {6}, pages = {13-17}, abstract = {Electromagnetically induced transparency (EIT) in an inhomogenously broadened medium consisting of h-type threelevel atoms has been analyzed. It is shown that the Lambda system can induce a transparency of the medium when the probe laser and the coupling laser have the same frequency detunings (including zero). Across the EIT window, the radial variation of the strong coupling laser radiation may lead to electromagnetically induced focusing or defocusing of the weak probe laser at separate probe frequency detuning points.} } @ARTICLE{ShepherdFD96, author = {Shepherd, S. and Fulton, D. J. and Dunn, M. H.}, title = {Wavelength dependence of coherently induced transparency in a Doppler-broadened cascade medium}, journal = {Phys. Rev. A}, year = {1996}, volume = {54}, pages = {5394-5399}, abstract = {The effect of changing the coupling laser transition, and hence the wavelength, on the coherently induced transparency seen by a probe beam in a Doppler-broadened cascade electromagnetically induced transparency (EIT) configuration is studied experimentally and theoretically. The transparency of the vapor is shown to be an effect not just of EIT, but of the varying Autler-Townes splitting for each velocity group within the vapor. Consequently, the best overall transparency for Rabi splittings less than the Doppler width is not at the position of matched coupling and probe wavelengths, but for coupling wavelengths less than that of the probe. } } @ARTICLE{LiX96, author = {Li, Y. Q. and Xiao, M.}, title = {Enhancement of nondegenerate four-wave mixing based on electromagnetically induced transparency in rubidium atoms}, journal = {Opt. Lett.}, year = {1996}, volume = {21}, pages = {1064-1066}, abstract = {We report an experimental observation of the enhancement of nondegenerate four-wave mixing (NDFWM) based on electromagnetically induced transparency (EIT) in a lambda-type three-level system of rubidium atoms. We measured both the linear susceptibility Im chi(1) over (D) (absorption) and the third-order nonlinear coefficient chi(3) over (D) separately for the NDFWM process at a low atomic density. We found that, owing to the EIT effect, the linear absorption term Im chi(1) over d(D) is greatly reduced, while the nonlinear generation term chi(3) over (D) is resonantly enhanced, permitting us to observe a significant enhancement of the NDFWM signal in an optically dense medium. (C) 1996 Optical Society of America.} } @ARTICLE{RiceB96, author = {Rice, P. R. and Brecha, R. J.}, title = {Cavity induced transparency}, journal = {Opt. Commun.}, year = {1996}, volume = {126}, pages = {230-235}, abstract = {We consider a two-level atom inside a cavity. We find that the absorption spectrum of the atom may exhibit a hole at line center for a weak probe. This hole appears when the cavity linewidth is small compared to the atom-field coupling strength, which is itself smaller than the atom's free space linewidth. In the weak-field limit, this system is analogous to a three-level atom, where similar absorption holes at line center occur due to electromagnetically induced transparency (EIT). In EIT, a strong field is required to strongly mix the upper two levels, whereas in the system we consider, it is the atom-field coupling strength that plays this role. An alternate explanation in terms of interference between the cavity field and atomic polarization is given. We also examine the driven cavity case. } } @ARTICLE{MoseleySFSD96, author = {Moseley, R. R. and Shepherd, S. and Fulton, D. J. and Sinclair, B. D. and Dunn, M. H.}, title = {Electromagnetically-induced focusing}, journal = {Phys. Rev. A}, year = {1996}, volume = {53}, pages = {408-415}, abstract = {The theoretical basis for electromagnetically-induced focusing (EIF), which is caused by spatial variations-in the coupling laser strength in an electromagnetically-induced transparency (EIT) experiment, is studied in detail. Using a numerical model it is shown that radial changes in both absorption and refractive index are important in predicting the probe beam's propagation conditions. Detailed calculations of the focusing and defocusing during EIF under various conditions are presented and compared with appropriate experiments. Diffraction like patterns are predicted for, and observed on, a probe beam after propagation through a smaller EIT aperture.} } @ARTICLE{FultonSMSD95, author = {Fulton, D. J. and Shepherd, S. and Moseley, R. R. and Sinclair, B. D. and Dunn, M. H.}, title = {Continuous-wave electromagnetically induced transparency - a comparison of v-system, lambda-system, and cascade systems}, journal = {Phys. Rev. A}, year = {1995}, volume = {52}, pages = {2302-2311}, abstract = {A theoretical and experimental investigation has been carried out into the viability of V-type, Lambda-type, and cascade systems within rubidium for the observation of electromagnetically-induced transparency (EIT), A Lambda-type system is also discussed where EIT is induced on a two-photon transition. Continuous-wave single-frequency titanium sapphire lasers have been employed to provide the applied optical fields. It is found that systems that have a strong coupling field resonant with the 5S(1/2) ground state suffer from complicating optical pumping mechanisms that tend to mask EIT windows. It is also found that wavelength matching of the applied optical fields enhances the observation of EIT since this results in a reduced residual Doppler linewidth of the atomic system. } } @ARTICLE{MoseleySFSD95, author = {Moseley, R. R. and Shepherd, S. and Fulton, D. J. and Sinclair, B. D. and Dunn, M. H.}, title = {2-photon effects in continuous-wave electromagnetically-induced transparency}, journal = {Opt. Commun.}, year = {1995}, volume = {119}, pages = {61-68}, abstract = {Electromagnetically-induced transparency (EIT) in a cascade three-level scheme is studied in rubidium vapour using continuous-wave titanium sapphire lasers. A counter-propagating experimental configuration significantly reduces the coupling laser power requirements and a reduction in absorption of over 90\% is observed. The hyperfine structure of the upper level is seen within the EIT feature and the application of EIT to highresolution two-photon spectroscopy is discussed. Simultaneous measurements of the excitation to the upper state are presented and clearly show Autler-Townes splitting and power broadening.} }