Home Forums FDTD Optiwave Designer

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• #20999
Kiki Kosma
Participant

How can I draw a 3D triangular waveguide? i.e. a waveguide which is triangular in the xy plane and runs along the z direction.
Thanks!

• #21002
Damian Marek
Participant

Hey,

Create a new channel profile with the profile designer. Choose the first layer and then check the slanted walls box. You can choose the slant angle to be steep enough to meet in the middle creating a point. I made an isosceles triangle in the pictures attached.

Cheers

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• #21027
Kiki Kosma
Participant

Thank you! I have another question regarding the simulation parameters. What is the difference in the results of a simulation between a CW input field and a Gaussian modulated CW input field? What is the spectral width of the input fields in the two cases?

• #21028
Damian Marek
Participant

I think you almost answered your own question.:) The spectral width of the CW input field is essentially zero, where as the spectral width of the Gaussian modulated CW input field can be quite large.

The half width of the spectral content is 1/T, the half width in time. For the default pulse, that corresponds to 54.8 THz half width at e^-0.5 the maximum. That means the bandwidth would be about 109 THz.

Gaussian Pulse Description [FDTD]

Cheers!

• #21029
Kiki Kosma
Participant

So one does choose a Gaussian modulated input field in order to play with the spectral bandwidth right? What confuses me though is the bandwidth of the resulting spectra after the simulation: Why do I get such a broadband result when I run a simulation with a CW input source?

• #22363
Kiki Kosma
Participant

Hello everyone, can anybody advise me on how one decides for how much time should a 3d simulation run in order to get some good results ? Thanks!

• #22380
Damian Marek
Participant

This can depend on the design and can be particularly challenging if you have a cavity, which traps the light within it. For your typical, reflection/transmission simulation you want to run the simulation long enough that the field begins to reach steady state, which generally means the electromagnetic field begins to reach 0 everywhere. You can take snapshots to see the relative magnitude of the field and wait until it becomes below 1% of the initial excitation.