In this post, we shall discuss about the inverse design of bullseye cavities for the optimization of Quality factors. Regular bullseye cavities (circular gratings formed by the periodical etching of rings from a substrate material) have Q-factors around 1000. Low-Q cavities have higher loss of photons, that can result in low-spin cooperativities. (https://pubs.acs.org/doi/10.1021/acs.nanolett.2c03098)
In this work, we shall try to increase the Q factor by optimizing the dimension of the bullseye structure by utilizing the power of inverse design. We perform this by design in the guided mode expansion domain, using the Legume package. Tidy3D does not yet have the Q factor inverse design functionality.
The codes have been collected in this github repository. (You can email me for the access of this repository)
The results are summarized in this google drive folder.
The optimized bullseye cavity structure as visualized in the Tidy3D GUI
Here is a comparison between optimized and regular bullseye spectrum
