Inverse Design of Ultra-Compact Passive Phase Shifters Using Multi-Objective Particle Swarm Optimization

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 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu m\times 3.2\mu m$</tex> 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.