Sudden reflectivity drop


    • Frederic Wu


      I want to know if this is a glitch in simulation or a design problem because I cannot think of a physics principle related to this phenomenon.

      The red blocks are silicon and the purple blocks are silicon oxide

      A DBR targeting 2.5 µm is provided below

      DBR targeting 2.5 µm

      • Reflected power

      • Transmitted power

      The problem I am facing currently is that when I add additional layers targeting 2.8µm below the original DBR that is targeting 2.5µm, there is a sudden drop in reflected power at around 3µm. Given that there are little transmission from the 2.5µm and that there are no cross-wavelength interference when using a DFT monitor, why is the reflected power affected when I add additional layers below the original DBR that targets 2.5µm? You can compare the above graphs with the graphs below. Please help me out, thanks.

      Stacked DBR with layers targeting 2.5µm above layers targeting 2.8µm:

      • Structure

      • Reflected power

      • Transmitted power

    • Guilin Sun
      Ansys Employee

      I believe this is how the DBR works. With certain thickness, it selects a wavelength to reflect. It is physical.

      If the desired wavelength is not exactly what you want, you may need to optimize it,

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