How do I add arbitary shapes to device

[joseph-at-sacher-laser]

I would like to add arbitrary shapes in to simulate.

I can't seem to find a proper way to do this, as an example, a NumPy array or GDSII file. How can I turn this imported object into a device to attempt inverse design?

[ymahlau]

Hello, you can do this in the following way:

• Add a fdtdx.Device structure to your simulation. It is best to give it a specific name attribute when initializing for the later steps. You can also add a mapping pipeline from parameters->material index optionally. By default the device maps zero to the material with lowest permittivity and 1 to the one with higher permittivity.
• run the place_objects function as usual, which returns among other things a params dictionary.
• inside the dictionary, you will find an entry for the name given to the device structure. You can update this with the parameters you would like to include in the simulation. Note that if you include any floating point values between 0 and 1 the resulting grid cell will contain an interpolated material.

For an example on how this can be done, look at the example script here: https://github.com/ymahlau/fdtdx/blob/main/examples/optimize_ceviche_corner.py

In the script, the parameters are also automatically optimized which may or may not be necessary for your use case.

Does this answer your question? If you encounter any problems please let me know

[joseph-at-sacher-laser]

Hi, Yannik,
Thank you so much for your response
I was thinking, how can I add this grating coupler.

https://gdsfactory.github.io/gdsfactory/components.html#gdsfactory.components.grating_couplers.grating_coupler_elliptical.

as a device in the setup attached

and attempt to focus the light onto the energy detector via inverse design.

So far I have been able to inverse design a metalens but want to try and optimise a grating coupler

[joseph-at-sacher-laser]

HI yannick,
Let me attempt what you suggested. I misunderstood your statement before the above response. Thanks, though.

[ymahlau]

Alright, let me know if any other questions come up