Liquid crystal-optical phased arrays (LC-OPA)-based optical beam steering with microradian resolution enabled by double gratings.

We demonstrate an optical beam steering setup based on a liquid crystal-optical phased array (LC-OPA) with high angular resolution and low beam divergence, due to the use of double-grating configuration to enhance the corresponding angular resolution of LC-OPA. The introduction of two nonparallel blazed gratings with a special included angle can achieve multiple diffractions for the incident light, leading to the realization of angular compression. Numerical simulation results show the angular compression ratio can be optimized by selecting the appropriate grating constant and the included angle of double-grating. Experimental results verify that the steered angle of the incident light can be compressed so that the angular resolution of the steered beam can correspondingly be improved more than six times. In addition, when the beam is multiply diffracted within the double-grating configuration, the divergence angle becomes smaller as the beam size is enlarged. Therefore, both the microradian steering resolution and the narrow beam divergence can be simultaneously obtained with our proposed setup. The efficiency of the steering where the beam diffracted four times within the double-grating configuration is 80%.