Rectangular input field

[Paulo Lourenco]

Hi guys,

Wonder you can help me…? Are there any constraints that should/must be observed when using a rectangular input field propagating inside a dielectric waveguide?
I have noticed in Lessons/Tutorials that the rectangular input field property is used when a non-guided plane wave simulation is the intended target (e. g. a plane wave incident on a surface…).

Thank you in advance.

[Scott Newman]

Hello Paulo

The issue you will have with the rectangular input field inside a dielectric waveguide is that the field profile will not match the modes of your waveguide so you will have odd propagation patterns and particularly strong evanescent fields.

When exciting a waveguide the more conventional approach would be to use the mode profile of the waveguide for excitation. This option is available to you through the modal , this is precisely what the modal option within Input Field Transvere section within the Input Plane source.

What kind of behaviour are you attempting to model? Coupling to a waveguide or propagation within the guide?

Scott

[Paulo Lourenco]

Hi Scott,

I want to model the propagation within a waveguide but, as far as I know, if this waveguide supports more than the fundamental mode you can only simulate each mode individually. What about if we want to model propagation within a multimode waveguide?

Thank you for answering.

[Scott Newman]

Hi Paulo,

It is true that if you use the mode excitation with the input plane you can only inject one mode. The solution is to use an input plane for each mode with the planes overlapping each other.

Attached you will see a very simple example with a 2um wide waveguide and 2 Input planes each injecting a different mode.

Let me know if you require further assistance,
Scott

[Paulo Lourenco]

Hi Scott,

I cannot find your attached file but I created a simple test and verified it. Thank you for the insight…

Best regards.

[Scott Newman]

Hi Pauolo,

There seems to have been an issue in uploading the file, my apologies. I am glad to hear you were able to set it up.

Scott

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