Bidirectional high sidelobe suppression silicon optical phased array

An optical phased array(OPA),the most promising non-mechanical beam steering technique,has great potential for solid-state light detection and ranging systems,holographic imaging,and free-space optical communications.A high quality beam with low sidelobes is crucial for long-distance free-space transmission and detection.However,most previously reported OPAs suffer from high sidelobe levels,and few efforts are devoted to reducing sidelobe levels in both azimuthal(φ)and polar(θ)directions.To solve this issue,we propose a Y-splitter-assisted cascaded coupling scheme to realize Gaussian power distribution in the azimuthal direction,which overcomes the bottleneck in the conventional cascaded coupling scheme and significantly increases the sidelobe suppression ratio(SLSR)in the φ direction from 20 to 66 dB in theory for a 120-channel OPA.Moreover,we designed an apodized grating emitter to realize Gaussian power distribution in the polar direction to increase the SLSR.Based on both designs,we experimentally demonstrated a 120-channel OPA with dual-Gaussian power distribution in both φ and θ directions.The SLSRs in φ and θ directions are measured to be 15.1 dB and 25 dB,respectively.Furthermore,we steer the beam to the maximum field of view of 25° × 13.2° with a periodic 2λ pitch(3.1 μm).The maximum total power consumption is only 0.332 W with a thermo-optic efficiency of 2.7 mW/π.