nTM = getsweepresult("sweep","neff"); # sweep is done for TM mode assuming symmetry
Heat = nTM.Heat;
Heat = transpose(Heat);
nTM = nTM.neff;
delta_nTM = nTM-nTM(1);

plot(Heat,real(delta_nTM),'Heater input (W/cm)','dneff');

outdata = [ Heat, real(delta_nTM), imag(delta_nTM) ];
format long;
filename = "delta_neff_vs_heat.txt";
if(fileexists("filename")) { rm(filename); }
write(filename,num2str(outdata));