High-efficiency and broadband photonic polarization rotator based on multilevel shape optimization

Abstract : We report on a novel photonic polarization rotator design obtained by multi-level shape optimization. The numerical method consists in a topological optimization scheme improving iteratively the efficiency of the component by modifying its shape on two discrete levels along the etching direction. We numerically show that, compared to the state of the art single level shape optimization, the performances can be drastically improved for a given device length. Next, the polarization conversion efficiency can be further improved up to a computed value of $\sim$98.5 % with less than 0.35 dB insertion losses on a 100 nm bandwidth for a 6 $\mu$m × 1 $\mu$m footprint.