Photonics

Photonics

different result for wavelength and frequency interplation TMM in FDTD

    • xiaofei.xiao15
      Subscriber

      I am using TMM for a very simple simulaiton, however, When I use two different definition for wavelength (method 1) and frequency (method 2), the results are very different. Why?

      thanks

      closeall;
      clear;

      # method 1
      lam0 = linspace(400e-9, 2000e-9,100); # frequency vector
      f = c/lam0; # frequency vector, why this one is not correct?

      # method 2
      #f = linspace(c/400e-9, c/2000e-9,100); # frequency vector
      #lam0 = c/f;

      theta = 0; # angle vector
      d = [0; 170e-6; 0]; # air/SiO2/Si/SiO2/air
      nf = length(f);
      nd = length(d);

      # refractive index of each layer (dispersive)
      n2 = matrix(nd,nf);
      n2(1,1:nf) = 1; # air
      n2(2,1:nf) = getfdtdindex("SiO2 (Glass) - Palik",f,min(f),max(f));
      n2(3,1:nf) = 1; # air

      RT2 = stackrt(n2,d,f,theta); # dispersive data index data, and theta from 0 to 45 deg

      visualize(RT2);

      plot(RT2.lambda*1e6,RT2.Rp,RT2.Rs,RT2.Tp,RT2.Ts,"wavelength (um)","Power","170um SiO2, theta=0");
      legend("Rp","Rs","Tp","Ts");

      R = RT2.Rp;
      T = RT2.Tp;
      matlabsave("170um_SiO2_R_T",lam0, R, T);

    • xiaofei.xiao15
      Subscriber

      this seems the high-frequency FP cavity interference because of the SiO2 slab. Can we eliminate these fringes? because in the experiment, we would not see them .

      thanks

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