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Check list of revising the transmission data in Bragg Grating Waveguide

    • Altair45

      I am working with Lumerical FDTD for the calculation of a coupled-resonator optical waveguide with Bragg grating. I am trying to extract the transmission and compare the data with the reference data as both are attached below. In this comparison, I'd like to match the reflection intensity from ~ -45dB to ~ -100dB like the reference. To do like this, what should I check the setting value or parameters in the FDTD simulation?

      First image is the motivated design in my FDTD simulation and second is my transmission data, and the last is reference data (Han, Changhao, et al. "Slow light silicon modulator beyond 110 GHz bandwidth." arXiv preprint arXiv:2302.03652 (2023).)

      I would appreciate any help and advice, 

      Thanks in advance

      Kang Seok Kim

    • Guilin Sun
      Ansys Employee

      This will need long simulation time, smaller autshotoff min, and proper PML settings, such as number of PML layers (in total about half wavelength thick). As you can see from your result, it has ripples, which indicates the actual simulation time is not long enough.

      Oce the curve is smooth, then you will need to use finer mesh, and keep PML away (half wavelength) from grating teeth.


      There are some fine-tuning works to be done.

      Please check this post for comparison: 

      Ansys Insight: Why my simulation result is different from published paper or experiment?


      Accurate frequency-domain result will need sufficient time and smaller autoshutoff min , as well as higher mesh accuracy, low PML reflection etc.




    • Altair45

      Thank you for your help. Following your advice, I have just set the value rightly now.

      • liyaqian

        Hello, did you use FDTD to simulate the entire 124um device? What's the duty cycle? Thanks!


        • Altair45

          Hello, while the duty cycle is not mentioned in this reference, I set the duty cycle to 0.5 arbitrarily. Thanks

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