Learning Forum

[Anjali A R]

I had been trying to calculate bending loss for a silicon waveguide. Initially, I tried with FEEM (the discussion is in the link: /forum/forums/topic/loss-vs-waveguide-bend-radius-in-lumerical-feem/).

Currently, I am trying to compare the results with that of the one obtained with EME. 

 I have followed the instruction in this post (/forum/forums/topic/is-it-possible-to-simulate-bent-waveguide-using-eme/) to check the bending loss using EME. I found that the loss for the same bend radius keeping varying with change in span of simulation region. 

The bending loss for 15 mm bent radius, as obtained from FEEM was 50 dB/cm, whereas EME gives different values as shown (for same settings, but different simulation region span).

Here, 44.7 dB/cm is the value obtained, which has been reduced to 7.8 dB/cm for a larger simulation span.

How much span should I keep while performing EME simulation? Please suggest what can be done.

Thank you.

 

[Amrita Pati]

Hi Anjali,

As you might have already read, the modes can interact with the PML Boundaries to create artificial loss/gain. Especially in a bent waveguide, where you see radiation in the direction opposite to the bend. I will recommend running a sweep for different values of the simulation span. It is hard to tell if we can trust any of the two results, until we perform a more systematic convergence testing. When you run a sweep, you will see that the after a certain point (simulation span), the losses become almost constant (converge) even when you increase the simulation region. Then you can use the point where the losses start converging as your final simulation region.

Regards,
Amrita

[Anjali A R]

Thank you, Amrita.

I will try out the suggestion.