Inverse-designed ultra-compact passive phase shifters for high-performance beam steering

Abstract

Ultra-compact passive phase shifters are inversely designed by the multi-objective particle swarm optimization algorithm. The wavelength-dependent phase difference between two output beams is originated from the different distance of the input light passing through the 4 µm×3.2 µm rectangular waveguide with random-distributed air-hole arrays. As the wavelength changes from 1535 to 1565 nm, a phase difference tuning range of 6.26 rad and 6.95 rad is obtained for TE and TM mode, respectively. Compared with the array waveguide grating counterpart, the phase shifters exhibit higher transmission and lower excess loss, with a much smaller footprint. By combining the inverse-designed phase shifter and random-grating emitter together, integrated beam steering structures are built, which show a large scanning range of ± 25.47° and ± 27.85° in lateral direction for TE and TM mode, respectively. This work may pave the way for the development of ultra-compact high-performance optical phased array LiDARs.