Learning Forum

[Deng Mao]

Hi there,

I am simulating a tapered SiN ridge waveguide structure. The core SiN has a height of 400 nm and slab SiN has a height of 270 nm. At the input side, the core and slab waveguide widths are both 1.15 um. At the output side, the core and slab widths are both linerly tapered to 1.4 and 2.8 um. The input side I am selecting the fundamental TE and TM modes. The output side I am selecting the 1-5 th order mode. When injecting the fundamental TE mode, the major crosstalks comes from the 4th and 5th order modes at the output ports. The results does not make sense to me. May I ask if there is anything in the setup I should modify?

Here is the IL results: (1,2 th mode is the input side, 3-7 are the output side modes)

Thank you,

Deng

[Niki Papachristou]

Hi Deng,

Thank you for reaching out to us. I believe that your results can be explained if you do a mode overlap analysis. Please have a look on this article: Understanding the mode overlap calculation. It seems that in your case modes 4 and 5 have a stronger overlap with mode 1 while they are guided into your tapered waveguide comparing to modes 2 and 3.

Kind Regards,

Niki