Bending loss in "rib" like waveguide


I am trying to simulate the bending loss for a strip waveguide that has a slab right above it of a different material, but essentially it is like an upside down rib waveguide. I find it difficult to get the bending loss as the mode goes into the slab quite a bit, so as I increase the domain even larger, the bending loss continues to change.

Attached is an example in log scale as well as the scipt file for the device/simulation.

Thank you!

Rib_Bending_Loss.lsf (1.5 KB)


I could not duplicate your result. However, I found that at such small bending radius, this waveguide does not support any modes:
linear scale:

log scale

maybe there are some difference for other settings.

please check the linear scale to see if the mode is supported. or attach your lms file here.

Thanks for trying to help! I should have specified that the advanced options setting “automatically remove pml modes” must be un-checked, and then the supported mode is actually mode# 6. It’s linear scale looks like this:

Thank you for letting me know this. When I checked that option, I got

loss 411.6 dB/cm;

then I change the mesh settings: you used fixed mesh points but when the span changes, the mesh size changes. I would suggest to fix the mesh size. when the mesh is 0.02um, x span is (the original one), I got

loss is 427dB/cm;

When I fixed the mesh size, and increase the xspan to be 55um, I got

If this is the mode you desired, it is obviously a leaky mode, which is very challenge to simulate accurately.

You may need to increase the PML layers to see if you can get a result with small change of the loss.

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Yes, that helps. Fixing the mesh size should help. Thank you!!