Inverse Design of Ultra-Compact and Low-Loss Optical Phase Shifters

In previous works, inverse design methods have primarily focused on manipulating the optical power to achieve specific design targets. In this paper, we use the inverse design method to enable the precise engineering of the optical phase. As a proof of concept, we present a series of phase shifters (PSs) with varying phase shifts, which are inversely designed and theoretically validated on the silicon-on-insulator (SOI) platform. The designed PSs exhibit remarkable accuracy, with deviations of below 1 & DEG;. These proposed PSs feature an ultra-compact footprint of 3 & mu;m in length and offer superior fabrication tolerances compared to conventional structures. Over the 1535-1565 nm bandwidth, the discrepancy between the actual and target phase shifts remains below & PLUSMN;1 & DEG; for all phase shifters, while the insertion loss is consistently below 0.035 dB. Moreover, the feasibility of the designed five PSs is verified using 2 x 2 multimode interference couplers (MMI).