nanotaper_overlap.lsf

# MODE Solutions script
#   do mode overlap calculations of gaussian beams with FDTD field

new; cleardcard;
FILE = "nanotaper";
loaddata(FILE);
addfde;

NA_list=0.1:0.02:0.9;
PLOT_misalignment = 0;
PLOT_modeprofiles = 0;
Polarization = 0;  # 0=TE, 90=TM;

wg_list=[180e-9];
t_list=[220e-9];
lambda_list=c/getdata('output','f');

write ('edgecoupler_FDTD.txt','FILE, WG_w, WG_t, Wavelength, Best NA, Best coupling');
for (l=1:length(t_list)) {
	for (k=1:length(wg_list)) {
		for (j=1:length(lambda_list)) {
			setanalysis('wavelength',lambda_list(j) );
			setanalysis('sample span',6e-6);
			setanalysis('number of plane waves', 200);
			edge_coupling=matrix(length(NA_list),1);
			gaussianbeams=matrix(length(NA_list)*2,1);
			setanalysis('polarization angle',Polarization); 
			setanalysis('beam direction','2D X normal');
			for (i=1:length(NA_list))  {
				setanalysis('NA',NA_list(i));	
				beam_name=createbeam; 
				cou=overlap('output','gaussian'+num2str(i),0,t_list(l)/2,0); 
				?edge_coupling(i)=cou(2);   # power coupling		
			}
			plot(NA_list, 10*log10(edge_coupling),'Lens NA', 'Coupling efficiency (dB)', FILE); 
			setplot ('y min', max ([ min( 10*log10(edge_coupling)), -4] )   );
			setplot ('y max',0);
			exportfigure(FILE+'(dB).jpg');

			best_coupling = max(10*log10(edge_coupling)); pos=find(10*log10(edge_coupling), best_coupling); best_NA = NA_list(pos);
			
			# calculate the fibre misalignment sensitivity
			if (PLOT_misalignment) {
				xlist=[-2:.1:2]*1e-6;
				x_misalign=matrix(length(xlist)); 
				y_misalign=matrix(length(xlist));
				for (m=1:length(xlist)) {
					cou=overlap('output','gaussian'+num2str(i), xlist(m), t_list(l)/2,0); x_misalign(m)=cou(2);
					cou=overlap('output','gaussian'+num2str(i), 0, t_list(l)/2+xlist(m),0); y_misalign(m)=cou(2);
				}	
				plot (xlist, x_misalign,y_misalign);
				legend('x_misalign','y_misalign');		
			}
			matlabsave ( FILE + '.mat' );
			write (FILE+'.txt',FILE+ ', '+num2str(wg_list(k)*1e9)+', '+num2str(t_list(l)*1e9)+', '+ num2str(lambda_list(j)*1e6) +', ' + num2str(best_NA)+', '+num2str(best_coupling)   );
		}
	}
}