# DESCRIPTION
# {
#     Modulation bandwidth is calculated from a small signal model implemented in script, with DC parameters derived from the 
#     full numerical simulation. To increase the accuracy of bandwidth calculation the capture/escape rate model is implemented 
#     based on 1992, Nagarajan, High speed quantum-well lasers and carrier transport effects.
#          
#     NOTES:
#       
#       1. Spontaneous emission contribution to the small signal photon density is neglected in the small signal model as it does not affect the 
#          modulation bandwidth significantly. This agrees with the reference (1992, Nagarajan).
#       2. The device model used in this example is our FP getting started example.
#
# }

clear;

small_signal_bandwidth; #load custom script function that implements small signal model.
load("TWLMexampleLaserFP300umCF353THzR3R3nel100_small_signal");
switchtolayout;
#Enable diagnostic output to inform the small signal model of DC operating point results
setnamed('TWLM_1','run diagnostic',true);
setnamed('TWLM_1','longitudinal profiles downsample factor',1000);
setnamed('TWLM_1','record carrier density profile',true);
setnamed('TWLM_1','record photon density profile',true);
setnamed('TWLM_1','record recombination rates profile',true);
#Enable carrier capture/escape rate model and set some reasonable values (not necessarily accurate for the device in question)
setnamed('TWLM_1','enable SCH',true);
setnamed('TWLM_1','well carrier capture rate',1.42857e+10);
setnamed('TWLM_1','well carrier escape rate',7.14286e+09);
setnamed('TWLM_1','total well thickness',1e-7);
setnamed('TWLM_1','total barrier thickness',1e-7);

run;

steadyStateTime = getnamed("::Root Element","time window");
ss_BW = ss_bandwidth(steadyStateTime,20e9,1000);
?'3dB bandwidth from small signal simulation is ' + num2str(ss_BW.bandwidth*1e-9) + ' GHz';
three_dB=log10(ones(length(ss_BW.rf_response))*0.001);
plot(ss_BW.freq*1e-9,ss_BW.rf_response,three_dB,"Frequency (GHz)", " Normalized response (dB)","","linewidth=2");
legend('small signal RF response','3dB cut-off');