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Beam Envelope vs Frequency Domain

Posted 20.07.2015, 08:20 GMT-4 Wave Optics, Modeling Tools & Definitions, Parameters, Variables, & Functions Version 5.0, Version 5.1 4 Replies

Silvio Mario Luciano Greco
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Hello everyone,
I have a big doubt about whether it's bettere to use the Beam Envelope or the Frequency Domain Physics to model an optical Add-Drop filter.
I need to simulate the behaviour of the coupling between a waveguide, in which the input wave is fed, a MicroRacetrack Resonator (MRR) and another waveguide from which it's possible to collect an output. I need to evaluate the coupling efficiency in a range of wavelengths (typically from 1500 to 1600 nm) and with varying MRR geometrical parameters.
The geometry is shown in the picture, the mesh has been set to Free Triangular with different maximum element size for the core (waveguides and MRR, silicon) and the cladding (air) material, depending on the refractive index.
I tried to follow the examples in the Model Library both for the FD and the BE physics but, while the former has a huge computational weight, the latter doesn't converge.
Any suggestion is appreciated.
Thanks.

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4 Replies Last Post 29.07.2015, 10:59 GMT-4
Walter Frei COMSOL Employee

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Posted: 9 years ago 20.07.2015, 16:20 GMT-4
Hello Silvio,

You will want to follow the approach outlined in this example:
www.comsol.com/model/optical-ring-resonator-notch-filter-22221

Also make sure to look at the meshing techniques outlined in this example:
www.comsol.com/model/mach-zehnder-modulator-15061

Best Regards,
Hello Silvio, You will want to follow the approach outlined in this example: http://www.comsol.com/model/optical-ring-resonator-notch-filter-22221 Also make sure to look at the meshing techniques outlined in this example: http://www.comsol.com/model/mach-zehnder-modulator-15061 Best Regards,
Silvio Mario Luciano Greco
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Posted: 9 years ago 21.07.2015, 11:41 GMT-4
Thanks for your kind answer. I am trying to replicate the example in my version of COMSOL (v5.0) but the function "Field Continuity" is not available due to its implementation in version 5.1: given that I cannot update it (I am not a system administrator), is there a way to overcome this limitation?
Thanks again.
Thanks for your kind answer. I am trying to replicate the example in my version of COMSOL (v5.0) but the function "Field Continuity" is not available due to its implementation in version 5.1: given that I cannot update it (I am not a system administrator), is there a way to overcome this limitation? Thanks again.
Walter Frei COMSOL Employee

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Posted: 9 years ago 21.07.2015, 15:08 GMT-4
Dear Silvio,

We do recommend that you upgrade to COMSOL 5.1 for this type of analysis, yes. This Field Continuity feature is newly implemented in 5.1, and the upgrade is available to all on-subscription users.
Dear Silvio, We do recommend that you upgrade to COMSOL 5.1 for this type of analysis, yes. This Field Continuity feature is newly implemented in 5.1, and the upgrade is available to all on-subscription users.
Silvio Mario Luciano Greco
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Posted: 9 years ago 29.07.2015, 10:59 GMT-4
Thank you, I just obtained the upgrade to 5.1 and I'm already working on my model.
I have found a strange behavior of the model: abs(ewbe.S21)^2 gives me many values greater than 1. I can't understand wether it's plainly wrong or there's something I can't understand in the way S-parameters work.
Thank you, I just obtained the upgrade to 5.1 and I'm already working on my model. I have found a strange behavior of the model: abs(ewbe.S21)^2 gives me many values greater than 1. I can't understand wether it's plainly wrong or there's something I can't understand in the way S-parameters work.

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