On-chip silicon optical phased array for two-dimensional beam steering

A 16-element optical phased array integrated on chip is presented for achieving two-dimensional (2D) optical beam steering. The device is fabricated on the silicon-on-insulator platform with a 250 nm silicon device layer. Steering is achieved via a combination of wavelength tuning and thermo-optic phase shifting with a switching power of $P_{\pi }=20\mathrm{mW}$ per channel. Using a silicon waveguide grating with a polycrystalline silicon overlay enables narrow far field beam widths while mitigating the precise etching needed for conventional shallow etch gratings. Using this system, 2D steering across a $20°\times 15°$ field of view is achieved with a sidelobe level better than 10 dB and with beam widths of $1.2°\times 0.5°$.