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% Illustrates the use of LaguerreGaussianE.m, decompose.m and recompose.m by
% defining an off-center Guassian beam (Fig. 1, Col. 1) and recomposing it
% in a basis of Laguerre Gaussians defined about the center on the figure.
% The recomposed beam is shown in Fig. 1, Col. 2, where we have used the
% first 40 Laguerre Gaussian modes. Figure 1, Col. 3 shows the
% difference between the recomposed beam and the original. Figure 2 shows
% the magnitude of the coefficients of the various modes in the
% decomposition.
ploton=[1 1];
overlaponly=0; showfigure=0;
clear domain;
screensize=0.1;
nptsr=50;
nptstheta=100;
accuracy=0.001;
n=400;
[rmesh,thetamesh,xmesh,ymesh]=polarmesh([0,screensize,nptsr],[0 2*pi nptstheta],'lin');
domain(:,:,1)=rmesh; domain(:,:,2)=thetamesh;
w=0.02;
R=-1e3;
lambda=1.064e-6;
q=q_(w,R,lambda);
deltax=1.5*w;
deltay=1.5*w;
wfactor=1;
if overlaponly
z1=LaguerreGaussianE([0,2,q_(w,R,lambda),lambda],xmesh,ymesh,'cart');
z2=LaguerreGaussianE([0,2,q_(w,R,lambda),lambda],xmesh,ymesh,'cart');
a=overlap(z1,conj(z2),domain,rmesh) %#ok<NOPTS>
if showfigure
figure(1);
subplot(221); h=pcolor(xmesh,ymesh,abs(z1).^2); shg; colorbar; axis square; set(h,'edgecolor','none');
subplot(222); h=pcolor(xmesh,ymesh,abs(z2).^2); shg; colorbar; axis square; set(h,'edgecolor','none');
subplot(223); h=pcolor(xmesh,ymesh,angle(z1)); shg; colorbar; axis square; set(h,'edgecolor','none');
subplot(224); h=pcolor(xmesh,ymesh,angle(z2)); shg; colorbar; axis square; set(h,'edgecolor','none');
end
return
end
zin=LaguerreGaussianE([0,0,q_(w*wfactor,R,lambda),lambda],xmesh+deltax,ymesh+deltay,'cart');
[coeffs,tmat]=decompose(zin,domain,'lg',n,[q,lambda,accuracy]);
disp(' '); disp('horizontal');
dispmat(abs(coeffs(:,:,1)));
disp(' '); disp('vertical')
dispmat(abs(coeffs(:,:,2)));
zout=recompose(domain,'lg',coeffs,[q,lambda,accuracy]);
if ploton(1)==1
figure(1);
subplot(331);
h=pcolor(xmesh,ymesh,abs(zin).^2); set(h,'edgecolor','none'); axis square; colorbar; drawnow; shg;
title('original intensity');
subplot(332);
h=pcolor(xmesh,ymesh,abs(zout).^2); set(h,'edgecolor','none'); axis square; colorbar; drawnow; shg;
title('recomposed');
subplot(333);
h=pcolor(xmesh,ymesh,abs(zout).^2-abs(zin).^2); set(h,'edgecolor','none'); axis square; colorbar; drawnow; shg;
title('difference');
subplot(334);
h=pcolor(xmesh,ymesh,real(zin)); set(h,'edgecolor','none'); axis square; colorbar; drawnow; shg;
title('original real part');
subplot(335);
h=pcolor(xmesh,ymesh,real(zout)); set(h,'edgecolor','none'); axis square; colorbar; drawnow; shg;
title('recomposed');
subplot(336);
h=pcolor(xmesh,ymesh,real(zout)-real(zin)); set(h,'edgecolor','none'); axis square; colorbar; drawnow; shg;
title('difference');
subplot(337);
h=pcolor(xmesh,ymesh,imag(zin)); set(h,'edgecolor','none'); axis square; colorbar; drawnow; shg;
title('original imaginary part')
subplot(338);
h=pcolor(xmesh,ymesh,imag(zout)); set(h,'edgecolor','none'); axis square; colorbar; drawnow; shg;
title('recomposed');
subplot(339);
h=pcolor(xmesh,ymesh,imag(zout)-imag(zin)); set(h,'edgecolor','none'); axis square; colorbar; drawnow; shg;
title('difference');
end
if length(ploton)>=2 && ploton(2)==1
figure(2);
coeffplotmat=[coeffs(:,end:-1:2,2),coeffs(:,:,1)];
ps=(-size(coeffs(:,:,2),1)+1:size(coeffs(:,:,1),1)-1);
ms=(0:size(coeffs(:,:,2))-1);
[psmesh,msmesh]=meshgrid(ps,ms);
h=pcolor(psmesh,msmesh,log10(abs(coeffplotmat))); axis square; colorbar; drawnow; shg;
title('Log_{10} of coefficients of the modes in the decomposition');
xlabel('m'); ylabel('p');
end
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