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// Example no.3.7
// To calculate (a) the photon lifetime, (b) the threshold current, and (c) the current required to generate a mean photon density of 8.5 × 10^21 m−3
// Page no.130
clc;
clear;
// Given data
w=3*10^(-6); // The active area width in meter
d=0.3*10^(-6); // The active area thickness in meter
L=500*10^(-6); // The length
Te=1*10^(-9); // Electron lifetime
Neth=0.8*10^(24); // Threshold electron density
aint=46*10^2; // Internal cavity loss in m^-1
n=3.5; // Refrective index of the medium
R1=0.65; // The reflectivity of ligth wave which is reflected at A
R2=0.65; // The reflectivity of ligth wave which is reflected at B
// (a)The photon lifetime
amir=(1/(2*L))*log(1/(R1*R2)); // The loss due to mirrors per m
c=3*10^8; // Speed of ligth in m/s
v=c/n; // Speed of ligth in medium (m/s)
Tp=1/(v*(aint+amir)); // The photon lifetime in sec
// Displaying the result in command window
printf('\n The photon lifetime = %0.2f ps',Tp*10^12);
// (b)The threshold current
V=w*d*L; //The active volume in m^3
q=1.602*10^(-19); //The electron charge in C
Te=10^-9; //The electron lifetime in sec
Ith=(Neth*q*V)/Te; //The threshold current in mA
// Displaying the result in command window
printf('\n The threshold current = %0.1f mA',Ith*10^3);
// The answer calculated in book is wrong
// (c)The current required to generate a mean photon density of 8.5 × 10^21 m−3
Nph=8.5*10^21; //Mean photon density
Tph=Tp; //The photon lifetime in sec
I=(Ith+(Nph*q*V)/Tph); //The current required to generate a mean photon density of 8.5 × 10^21 m−3
// Displaying the result in command window
printf('\n The current required to generate a mean photon density of 8.5 × 10^21 m^-3 = %0.2f mA',I*10^3)
// The answer calculated in book is wrong
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