{"id":311817,"date":"2023-10-17T13:23:27","date_gmt":"2023-10-17T13:23:27","guid":{"rendered":"\/forum\/forums\/topic\/how-to-deal-with-abrupt-transitions-in-eme-to-reduce-expansion-error\/"},"modified":"2023-10-17T13:23:27","modified_gmt":"2023-10-17T13:23:27","slug":"how-to-deal-with-abrupt-transitions-in-eme-to-reduce-expansion-error","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/how-to-deal-with-abrupt-transitions-in-eme-to-reduce-expansion-error\/","title":{"rendered":"How to deal with abrupt transitions in EME to reduce expansion error?"},"content":{"rendered":"

I am studying a vertical taper system where light couples from a waveguide from below to a top waveguide. To do so I am using a linear taper on the top waveguide like below. However I kept running into problems with respect to mode convergence: I would end up needing a lot of modes, which didn’t make much sense. I started looking into the expansion error and found that there is a huge peak on the transition at the thin end of the taper. <\/p>\n

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In an atempt to minimize this error I decided to add a new cell group surrounding this abrupt transition and calculate in this reagion 100 modes. Therefore, for this new simplified version I have a first group cell which is just a simple propagation through 10um and then a small group cell of 20nm that encompasses the abrupt transition. Despite achieving mode congergence according to the mode convergence sweep tool, I still get a big error on the mode expansion through the global diagnostics data set. Can anyone comment on the the expansion error? The only information I found was in here (Understanding EME error diagnostics – Ansys Optics<\/a>) from which I throught I had understood as projecting the mode on the left to the basis on the right and see how well it would be represented on the mode basis on the right. However, the fact that the value I get seems to be independent of how many modes I decide to use has me confused. <\/p>\n

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