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Calculate Relative intensity noise using Rate equations

  1. Dec 5, 2012 #1
    Hello Everybody,

    I'm trying to plot the frequency spectrum of RIN using Matlab.

    I've the following code

    function p=rateblock
    tau_s = 3e-9;
    N0 = 1e24;
    A =1e-12;
    P0 = 1/(A*tau_s);

    TSPAN = 0:1e-2:10.23;;
    Y0 =[0 0];

    [T,Y] = ODE45(@rate_equation,TSPAN,Y0);
    subplot(2,1,1)
    plot(T*tau_s ,Y(:,1)*N0)
    title('carriers density in high laser level')
    subplot(2,1,2)
    plot(T*tau_s ,Y(:,2)*P0)
    title('photons density in activer region') %

    dt=1e-2;
    s_avg=sum(Y(:,2))/1024;%average photon numbers
    ds=Y(:,2)-s_avg;%photon fluctuation with respect to average
    TT=1e-6; %total time of integration
    N=1024;%fft length
    F=[0:N-1]';
    RIN=((dt^2)/((s_avg)^2*TT)).*(abs(fft(ds))).^2;
    RIN=10*log10(RIN);
    plot(F,RIN)
    title('RIN')

    And for the Rate equation i used this function
    function dy = rate_equation(t,y)
    dy = zeros(2,1);

    tau_s = 3e-9; % carriers lifetime
    tau_p = 1e-12; % photons lifetime
    A = 1e-12; % linear gain costant
    N0 = 1e24; % trasparency carries density
    V = 3.75e-14; % modal volume
    gamma = 1e-5; % gain compression factor
    q = 1.6e-19; % electron charge

    I0 = N0*q*V/tau_s; % trasparency current
    tau_norm = tau_s/tau_p;
    eta = A*tau_p*N0; % efficiency

    I = 2.5*I0; % pumping current

    dy(1)= I/I0 -y(2)*(y(1) - 1) -y(1);
    dy(2) = tau_norm*(y(2)*(eta*(y(1) - 1) -1) + gamma*eta*y(1))


    Although I'm facing problems with caluclating the RIN and plot it with frequency ...

    Can anybody help me with this issue?
     
  2. jcsd
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