Photonics

Photonics

Optimization of focal spot intensity not behaving as expected.

    • williamfraser3
      Subscriber

      I have created a project in FDTD where I am trying to optimize some parameters of a metasurface to maximize the intensity of the E field at the focal spot. I have a point frequency-domain field and power monitor positioned at the center of the focal spot. In the optimizer, I have the E result from this monitor set as the figure of merit in the Setup tab then I use the following line to calculate the intensity as fom in the figure of merit script.

      fom = sum(abs(E)^2);

      I let it run overnight and it seemed stuck at 1 for a while until the fom shot up to 25:

    • Greg Baethge
      Ansys Employee

      Thank you for posting your question. I tend to find the custom figure of merit a bit tricky to troubleshoot, sometimes, so I would suggest to use "model" as an analysis group, to calculate the custom FOM there and use it directly in the optimization task. I think it is easier and you can check the figure of merit is properly calculated just by running the simulation and checking its value.
      I hope this will help!
    • Guilin Sun
      Ansys Employee
      In this case, please use the same result as the FOM. In the Optimization GUI it shows the best parameters. Please make sure you used the exact values shown there. If problem still exists, please send us an email with file attached with this post link.
    • williamfraser3
      Subscriber
      This fixed my problem. Thank you!
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