Photonics

Photonics

Absorption measurement

    • sreejyothi11
      Subscriber

      Hi,

      I am trying to obtain the absorption spectra of freely suspended monolayer MoSe2 and compare it with the simulated result in a paper (red curve in the graph). I used exactly the same permittivity data as in the paper. However, I see a significant difference in the spectra as shown below. I tried varying the meshing but didn't see any change in result. The material fit is also proper. Could you please tell me what are the other factors that could cause this difference.

    • Guilin Sun
      Ansys Employee

      for this freely suspended monolayer, how long is it? is it  a short section, or infinitely long?  what boundary conditions you are using?

      if it is a short section, you can use TFSF+PML;

      If it is infinitely long in terms of simulation ,you can use plane wave +periodic BCs, and get 1-R-T. It seems from the above result it is this case. Then next thing to do is to check if the mesh is proper.

      Do you use 2D sheet or 3D geometry? in both case you need to check the mesh to see if it is finer enough.

      When mesh is fine, please check PML  and make sure it is at least half wavelength away.

      Does this structure have strong reflection? if so, you may need to place the reflection monitor in between the source and the front sufrace. Please refer  https://optics.ansys.com/hc/en-us/articles/360034915753-Tips-for-accurately-measuring-reflection-in-an-FDTD-simulation

      Finally, please make sure the autoshutoff min is small enough. The default value is 1e-5, but you may further reduce it to 1e-6. This assumes the simulation terminates early, less than 100% in the process bar or in the log file. If it terminates at 100%, you will need to significantly increase the simulation time, and let the autoshutoff min to determine when to terminate the simulation.

      There are  other factors to be checked when comparing with publications: https://forum.ansys.com/forums/topic/ansys-insight-why-my-simulation-result-is-different-from-published-paper-or-experiment/

      Please try and see if it improves.

       

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