Learning Forum

[bartu.yaman]

Hello,

I am working on an edge coupler design where on the facet I have Si substrate + cladding + waveguide + cladding + air and I want to optimize the mode overlap with a fiber that has a large core size, i.e. large mode field diameter. The problem is that I need to make the FDE region quite large to capture fiber modes accurately, but doing so makes it inevitable to include the Si substrate in the simulation region which results in light getting trapped inside the Si substrate, giving me useless simulation results. I am looking for a way to work around this problem so that I can capture the modes in my facet and fiber at the same time accurately with light confined in the waveguide and not in the substrate. Is there a way to confine the light into the waveguide without removing the Si subrate or using the cladding everywhere inside the simulation region? 

 

Thanks in advance.

[Amrita Pati]

Hi Bartu,

I believe the mode you are seeing in the Silicon substrate is not physical and I believe most likely because of the interaction with the boundaries. Would you be able to share a screenshot of the mode distribution (where some of the energy is in the substrate)? I believe for the initial fiber position optimization, you can perform the overlap analysis without the presence of the substrate (disable the substrate) to avoid the spurious modes. This approach has also been adopted in one of our examples: Edge Coupler

Regards,
Amrita