Back reflection from port object

cohen26cohen26 Member Posts: 3

Hi,

I am wondering how to get rid of back reflection from a port injecting the fundamental mode into a waveguide. An image of the issue is shown here. I have not done an extreme amount of convergence testing, but the spacing from waveguide to edge in x,y,z directions is greater than 1um, the mesh is 10nm in x,y,z, I'm using stabilized PML and the input port object spans the entire x,z FDTD region. There used to be a lumerical forum where an answer was given but I see that its taken down now. Any help would be appreciated.


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Answers

  • kjohnsonkjohnson Posts: 175Ansys Employee

    Hello @cohen26 ,

    From the image it looks like the reflection is occurring at the PML boundaries, not from the port itself. Is the waveguide extended all the way through the PML boundaries? If it's not, the reflection could be from the end of the waveguide.

  • cohen26cohen26 Posts: 8Member

    Hi @kjohnson - yes, the waveguide is fully extended through the PML region and goes further outside the end of the PML/FDTD region as well.

  • kjohnsonkjohnson Posts: 175Ansys Employee

    I'm not sure what the problem would be. It's possible that this is due to an improperly injected source, but this reflection is more significant than I would expect with a source injection error. Could you please provide some more screenshots of the setup of the simulation? For example, the settings of the port and boundary conditions.

    It might also help to place a movie monitor over the simulation to help determine where the reflection occurs in the time domain.

  • cohen26cohen26 Posts: 8Member

    I have placed a movie object and am running - will update with results. Here are some images. The xy plane shows that the port is 3.5um from the FDTD boundary. The xz plane shows 1.2um from top/bottom of waveguide to FDTD boundary. Input waveguide cuts through the FDTD boundary. Simulation time is very large - just reaching autoshutoff level.

  • kjohnsonkjohnson Posts: 175Ansys Employee

    Hello @cohen26 ,

    Unfortunately Ansys staff aren't permitted to download files from the ALF, including images. Could you please paste the images directly onto your post, similar to what you did in your first post?

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