Creating non-standard 3D lattices in OptiFDTD designer

[Yameng Cao]

Hello,
I am trying to simulate dielectric rods, using optiwave’s language they are defined as “True 3D cylinders”, these cylinders have the same radius from top and bottom. In real like, etch is not ideally anisotropic, there could be underetch or overetch as depicted in the figure I attached. I am trying to lay down the design for the latter two “imperfect” cases, but am struggling to do so.

When I try to edit the lattice parameters, I can change the radius and height, but I actually want to use a function to change the radius with the height, so its wider on one end compared to the other. Something like Radius=constant*Yposition, where Yposition is the vertical coordinates in my design, but the problem is accessing the “Yposition” information.

Does anyone have an idea what I could do in this case?

Thank you

Yameng

[Damian Marek]

Yameng,

Try a 3D Rectangular Lattice with #A 5, #B 5, #C 1 and lattice scale of 2. Now add a new Atom and make it a Linear Taper Waveguide using the default Profile: WG_Fiber_Example. You can set the length and Taper characteristics to make a 3D model as below.

[Yameng Cao]

Thanks Damian, That’s the shape i’m gunning for! But is there a way to rotate by 90 degrees so its symmetry axis is along y?

[Damian Marek]

You can change the azimuthal angle by 90 degrees in the photonic crystal, if that isn’t the direction you want you might need to change your other geometries in the problem because of the way the waveguides are defined.

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