Design and analysis of a two-dimensional large-scale silicon-photonic optical phased array

Abstract

Currently, two-dimensional (2D) optical phased arrays (OPAs) have broad development prospects in many emerging fields. However, a traditional 2D-OPA sets a phase shifter for each antenna, causing large antenna spacing, high power consumption, and complex wiring. In this study, we first introduce a theoretical model of an N × N OPA by separating the phase shifter from the antenna element; only 2N phase shifters are used to realize 2D beam scanning, effectively reducing the power consumption and wiring complexity. To reduce the antenna spacing, we next use inverse design and particle swarm optimization to design compact, low-loss, and high-performance silicon-photonic devices, including cross waveguides, Y branches, directional couplers, and grating antennas. For the thermo-optic phase shifter (TOPS), we introduce the semiconductor material AlN that enables the modulation speed to reach 45 kHz. The length of the TOPS is 30 μm and phase-shifting efficiency (Pπ) is only 20 mW. Finally, for proof of concept, we built an 8 × 8 OPA architecture model with an antenna spacing of 8.5 μm. The simulation results show that the OPA achieves 10.5° × 10.5° 2D-beam steering at the 1.55-μm wavelength using only 16 TOPSs, and we use genetic algorithm to realize the sparse uniform array and achieve the side-lobe rejection ratio of 18 dB in the field of view.