Learning Forum

[10172100207]

Why does Lumerical example(defect scattering) use the difference of two cone volume integrals to obtain the scattered power in the PSL.lsf script?

the model:

 

Here is the script: 

############################################

# file: psl_analysis

# Description: This file is used to calculate

# the scattering from PSL spheres. It runs

# a reference simulation as well as the defect

# simulations.

# After the simulations are complete, the far

# fields are calculated. The reference far field

# is subtracted from the defect far field,

# giving the scattered far field.

#

# Copyright 2010 Lumerical Solutions Inc

############################################

 

polarization = "P"; #sets which polarization to run: "P", "S", "C" (circular)

 

run_simulations = 1; # set to 0 to analyze previously run simulations

 

 

 

if (run_simulations) {

switchtolayout;

 

if (polarization=="P") {

setnamed("FDTD","x",1e-6);

setnamed("source1","polarization angle",0);

setnamed("source1","angle theta",70);

setnamed("FDTD","y min bc","Symmetric");

select("source2");

delete;

}

if (polarization=="S") {

setnamed("FDTD","x",1e-6);

setnamed("source1","polarization angle",90);

setnamed("source1","angle theta",70);

setnamed("FDTD","y min bc","Anti-Symmetric");

select("source2");

delete;

}

if (polarization=="C") {

setnamed("FDTD","x",1e-6);

select("source2");

delete;

setnamed("source1","polarization angle",0);

setnamed("source1","angle theta",0);

setnamed("FDTD","x",0);

select("source1");

copy;

set("name","source2");

set("polarization angle",90);

set("phase",90);

setnamed("FDTD","y min bc","PML");

}

 

runsweep;

save;

}

 

swp="sweep_rad";

farfieldfilter(0.5);

 

# get the data from the sweep

E2_far=getsweepresult(swp,"E2_far");

T=getsweepresult(swp,"T");

SP=getsweepresult(swp,"SP");

rad = E2_far.rad;

res = length(E2_far.ux);

E2=E2_far.E2_far;

#plot(rad*1e9,log10(T.T*SP.SP),"radius (nm)","scattered power (log10, Watts)"

scat_power=matrix(length(rad)); #创建矩阵存储不同半径的scat_power

 

for (i=1:length(rad)) {

 

P_far_scat = sqrt(eps0/mu0) * pinch(E2(1:res,1:res,i));

scat_power(i) = 0.5*(farfield3dintegrate(P_far_scat,E2_far.ux,E2_far.uy,72,0,0)-farfield3dintegrate(P_far_scat,E2_far.ux,E2_far.uy,25,0,0));

image(E2_far.ux,E2_far.uy,pinch(P_far_scat)/pinch(max(P_far_scat)),"ux","uy","far field","plot polar");

}

 

savedata("psl_"+polarization,scat_power); # save data to an ldf file

 

 

 

# plot results from P,S,C polarization on same plot (if results exist)

if (fileexists("psl_p.ldf")) { loaddata("psl_P"); spP = scat_power; } else { spP = 0; }

if (fileexists("psl_s.ldf")) { loaddata("psl_S"); spS = scat_power; } else { spS = 0; }

if (fileexists("psl_c.ldf")) { loaddata("psl_C"); spC = scat_power; } else { spC = 0; }

 

if (spP==0 ) {spP=0*rad; }

if (spS==0 ) {spS=0*rad; }

if (spC==0 ) {spC=0*rad; }

 

plot(2*rad(1:length(rad))*1e9,log10(spP),log10(spS),log10(spC),"Diameter (nm)","log10(scattered power)");

legend("P","S","Circular");

My problem: 

scat_power(i) = 0.5*(farfield3dintegrate(P_far_scat,E2_far.ux,E2_far.uy,72,0,0)-farfield3dintegrate(P_far_scat,E2_far.ux,E2_far.uy,25,0,0));

Why does it use the power with a half-angle of 72 degrees minus the power with a half-angle of 25 degrees? How are the values of 72 and 25 determined?

[Amrita Pati]

Hello,

This was done to validate the results of the simulation against experimental data. If you go into the cited paper, you will find the following:

Let me know if you have any further questions.

Regards,
Amrita