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Optical

Waveguide simulation in fdtd solution

    • zahra mansouri
      Subscriber

       

      i am working on waveguide simulation in fdtd and mode solution lumerical. i have a cylinderical waveguide. with mode solution i get the neff and so i have propagation lenght of that. then i design the waveguide in fdtd solution and i use mode source for exciting a special mode that i calculateed propagation lenght for it. but here i cant see the propagation lenght that i calculated in previous step.

      my designed propagation lenght is 2 micron. in fdtd i draw a 4micron lenght waveguide and i excite it with only one mode but i cant see attenuation of wave.

      can anyone help me?

       

      i am working on waveguide simulation in fdtd and mode solution lumerical. i have a cylinderical waveguide. with mode solution i get the neff and so i have propagation lenght of that. then i design the waveguide in fdtd solution and i use mode source for exciting a special mode that i calculateed propagation lenght for it. but here i cant see the propagation lenght that i calculated in previous step.

      my designed propagation lenght is 2 micron. in fdtd i draw a 4micron lenght waveguide and i excite it with only one mode but i cant see attenuation of wave.

      can anyone help me?

       

    • Guilin Sun
      Ansys Employee

      what is the effecgtive index of the mode you used?

      Please check if the mode is truncated by PML. If so you will need to increase the simulation span.

      In addition, did you let the simulation run long enough and terminate it when the autoshutoff min is reached? you cannot simply use t=neff*L/c, since the source is a pulse.

      You will also need to extend the waveguide outside of PML.

      Without screnshots of your simulation settings, I just give the above recommendation. Please try.

       

       

      • zahra mansouri
        Subscriber

         

        dear Guilin Sun

        thank you for your reply. i will applied them on my project. i attached my simulation file here.

        the effective index of excited mode is 2.82956+0.0494307i.

        i would be thankful if you check this file.

         

         

    • Guilin Sun
      Ansys Employee

      We are not allowed to download or check customer simulation files in this forum. Since the mode is lossy, it is normal that the field is attenutated. You can calculate it in theory. However, discretization will introduce numerical error.

      • zahra mansouri
        Subscriber

        i shared a pdf file that contained my simulation shape and settings. in this simulation i used standard pml setting but i also simulated this file for higher pml profile before and the answers hasnt been changed.
        the problem is that i cant see calculated propagation lenght along the waveguide. i calculate the propagation lenght 2.4 micron but i cant see wave attenuation in that lenght. i use this below relation for calculating propagation lenght(pl).


        pl=1/(2*im(beta))


        beta= 2*pi*neff/lambda;

        https://drive.google.com/file/d/1o-BtV7o2jj8G5ONvwTqR2BZ90sCi9Y7S/view?usp=share_link

    • zahra mansouri
      Subscriber

      my project is a cylinderical mim waveguide and i used a magnetooptic material for dielectric layer. when i replace the magnetooptic layer by a isotropic dielectric the lumerical answers seems to be true. i can see the propagation lenght of waveguide when i simulate my project in fdtd 3d simulation.  

      can i use the fdtd 3d simulation for observing wave propagation when i used anisotropic material?i defined my material using the code explained on the Lumerical website. the wavelenght is 1550 nano and propagation lenght is about 4 micron. cylinderical radius is about 500 nano

    • Guilin Sun
      Ansys Employee

      You can add paramagnetic material in Material BASE and choose anisotropic:

       

      If it is for simple propgation in a straight waveguide, it is not necessary to simulate, as the mode will give you the propagation constants.

      • zahra mansouri
        Subscriber

        i have found the propagation constant and propagation modes with lumerical mode solution but i need to show the wave propagation of a one of the modes along the waveguide.

    • Guilin Sun
      Ansys Employee

      Then you can do FDTD simulatioon. Make sure the mode profile is not truncated otherwise it will cause diffraction.

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