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<?xml version="1.0"?>
<simulation xmds-version="2">
<name>Shahriar_system</name>
<author>Eugeniy Mikhailov, Simon Rochester</author>
<description>
License GPL.
Solving 3 level atom in double drive configuration
after Shahriar paper about white cavity
with field propagation along spatial axis Z
no Doppler broadening.
All fields detuned from upper level i.e. Raman configuration
*
* .....
* / ....
* / .... \
* / / \
* / /-------- |3>
* E3 / \
* / E2 \
* / / \ E1
* ------ |2> \
* \
* ------- |1>
*
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
IMPORTANT simplification: E2 = E3 by magnitude then we can use a field consisting
of beat note between E1 and E2 oscillating at frequency wa=(w1+w2)/2
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
We are solving
dE/dz+(1/c)*dE/dt=i*eta*rho_ij, where j level is higher then i.
Note that E is actually a Rabi frequency of electromagnetic field not the EM field
in xmds terms it looks like
dE_dz = i*eta*rhoij - 1/c*L[E], here we moved t dependence to Fourier space
VERY IMPORTANT: all Rabi frequency should be given in [1/s], if you want to
normalize it to something else look drho/dt equation.
No need to renormalizes eta as long as its express through i
the upper level decay rate in the same units as Rabi frequency.
</description>
<features>
<globals>
<![CDATA[
const double pi = M_PI;
const double c=3.e8;
const double lambda=794.7e-9; //wavelength in m
const double N=2e10*(1e6); //number of particles per cubic m i.e. density
const double Gamma_super=6*(2*M_PI*1e6); // characteristic decay rate of upper level used for eta calculations expressed in [1/s]
const double eta = 3*lambda*lambda*N*Gamma_super/8.0/M_PI; // eta constant in the wave equation for Rabi frequency. Units are [1/(m s)]
// repopulation rate (atoms flying in/out the laser beam) in [1/s]
const double gt=0.01/2 *(2*M_PI*1e6);
// Natural linewidth of the upper level [1/s]
const double G=2*6 *(2*M_PI*1e6);
// total decay of i-th level branching ratios. Rij branching of i-th level to j-th
const double R31=0.5, R32=0.5;
complex E1c, E2c, E3c, Efc; // Complex conjugated Rabi frequencies
complex r21, r31, r32; // density matrix elements
]]>
</globals>
<benchmark />
<arguments>
<!-- Rabi frequency divided by 2 in [1/s] -->
<!--probe-->
<argument name="E1o" type="real" default_value="0.0025*(2*M_PI*1e6)" />
<!--pump fields-->
<argument name="E2o" type="real" default_value="1.0*(2*M_PI*1e6)" />
<argument name="E3o" type="real" default_value="1.0*(2*M_PI*1e6)" />
<!-- Fields detuning in [1/s] -->
<!-- probe field detuning-->
<argument name="d1" type="real" default_value="12*(2*M_PI*1e6)" />
<!-- averaged detuning of pump fields i.e. mid point -->
<argument name="da" type="real" default_value="12*(2*M_PI*1e6)" />
<!-- detuning of pump fields with respect to each other -->
<argument name="delta" type="real" default_value="6*(2*M_PI*1e6)" />
<!-- incoherent pumping rate from level |1> to |3> in [1/s]-->
<argument name="gp" type="real" default_value="2*2.0*(2*M_PI*1e6)" />
</arguments>
<bing />
<fftw plan="patient" />
<openmp />
<auto_vectorise />
</features>
<!-- 'z' and 't' to have dimensions [m] and [s] -->
<geometry>
<propagation_dimension> z </propagation_dimension>
<transverse_dimensions>
<dimension name="t" lattice="10000" domain="(-2.0e-6, 4.0e-6)" />
</transverse_dimensions>
</geometry>
<!-- Rabi frequency -->
<vector name="E_field" type="complex" initial_space="t">
<components>E1 Ef</components>
<initialisation>
<![CDATA[
// Initial (at starting 'z' position) electromagnetic field does not depend on detuning
// as well as time
E1=E1o*exp(-pow( ((t-0.0)/1e-6),2) );
// very dirty hack, I assume that E2=E3 then I can use beatnote formula since
// w1 approcimately equals w2
// I assign it to new combined field with amplitude Ef
// E*cos( (wa+d/2)*t ) * E*cos( (wa-d/2)*t ) = 2*E*cos(d*t/2)*cos(wa*t) = Ef*cos(wa*t)
Ef = 2*E2o*cos(delta*t/2); // E3o assumed to be equal E2o
]]>
</initialisation>
</vector>
<vector name="density_matrix" type="complex" initial_space="t">
<components>r11 r22 r33 r12 r13 r23 </components>
<!--
note one of the level population is redundant since
r11+r22+r33=1
-->
<initialisation>
<![CDATA[
// Note:
// convergence is really slow if all populations concentrated at the bottom level |1>
// this is because if r11=1, everything else is 0 and then every small increment
// seems to be huge and adaptive solver makes smaller and smaller steps.
// As quick and dirty fix I reshuffle initial population
// so some of the population sits at the second ground level |2>
// TODO: Fix above. Make the equation of motion for r11
// and express other level, let's say r44
// through population normalization
r11 = 1; r22 = 0; r33 = 0;
r12 = 0; r13 = 0;
r23 = 0;
]]>
</initialisation>
</vector>
<sequence>
<!--For this set of conditions ARK45 is faster than ARK89-->
<integrate algorithm="ARK45" tolerance="1e-5" interval="10e-2">
<!--SIC algorithm seems to be much slower and needs fine 'z' step tuning and much finer time grid-->
<!--For example I had to quadruple the time grid from 1000 to 4000 when increased z distance from 0.02 to 0.04-->
<!--<integrate algorithm="SIC" interval="4e-2" steps="200">-->
<samples>200 200</samples>
<operators>
<operator kind="cross_propagation" algorithm="SI" propagation_dimension="t">
<integration_vectors>density_matrix</integration_vectors>
<dependencies>E_field</dependencies>
<boundary_condition kind="left">
<![CDATA[
r11 = 1; r22 = 0; r33 = 0;
r12 = 0; r13 = 0;
r23 = 0;
]]>
</boundary_condition>
<![CDATA[
E1c = conj(E1);
Efc = conj(Ef);
r21=conj(r12);
r31=conj(r13);
r32=conj(r23);
// Equations of motions according to Simon's mathematica code
dr11_dt = gt - 2*(gp + gt)*r11 - E1*i*r13 + E1c*i*r31 + G*r33;
dr12_dt = (-gp - 2*gt - d1*i + da*i)*r12 - Ef*i*r13 + E1c*i*r32;
dr13_dt = -(E1c*i*r11) - Efc*i*r12 + (-G - gp - 2*gt - d1*i)*r13 + E1c*i*r33;
dr22_dt = gt - 2*gt*r22 - Ef*i*r23 + Efc*i*r32 + G*r33;
dr23_dt = -(E1c*i*r21) - Efc*i*r22 + (-G - 2*gt - da*i)*r23 + Efc*i*r33;
dr33_dt = 2*gp*r11 + E1*i*r13 + Ef*i*r23 - E1c*i*r31 - Efc*i*r32 - 2*(G + gt)*r33;
]]>
</operator>
<operator kind="ex" constant="yes">
<operator_names>Lt</operator_names>
<![CDATA[
Lt = i*1./c*kt;
]]>
</operator>
<integration_vectors>E_field</integration_vectors>
<dependencies>density_matrix</dependencies>
<![CDATA[
dE1_dz = i*eta*conj(r13) -Lt[E1] ;
dEf_dz = i*eta*conj(r23) -Lt[Ef] ;
]]>
</operators>
</integrate>
</sequence>
<!-- The output to generate -->
<output format="binary" filename="Shahriar_system.xsil">
<group>
<sampling basis="t(1000)" initial_sample="yes">
<dependencies>E_field</dependencies>
<moments>I1_out If_out</moments>
<![CDATA[
I1_out = mod2(E1);
If_out = mod2(Ef);
]]>
</sampling>
</group>
<group>
<sampling basis="t(100)" initial_sample="yes">
<dependencies>density_matrix</dependencies>
<moments>
r11_out r22_out r33_out
r12_re_out r12_im_out r13_re_out r13_im_out
r23_re_out r23_im_out
</moments>
<![CDATA[
// populations output
r11_out = r11.Re();
r22_out = r22.Re();
r33_out = r33.Re();
// coherences output
r12_re_out = r12.Re();
r12_im_out = r12.Im();
r13_re_out = r13.Re();
r13_im_out = r13.Im();
r23_re_out = r23.Re();
r23_im_out = r23.Im();
]]>
</sampling>
</group>
</output>
</simulation>
<!--
vim: ts=2 sw=2 foldmethod=indent:
-->
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