Two-dimensional optical phased array with grating lobe suppression by element distribution and emitting amplitude optimization

Abstract

A grating-lobe-suppressed two-dimensional (2D) optical phased array (OPA) is proposed to realize optical beam steering based on unequally-spaced technique, in which the element distribution is optimized by a modified genetic algorithm to achieve a minimum peak side-lobe level (PSLL). Numerical simulations of 2D unequally-spaced OPAs are carried out. The results show that by optimizing the element distribution in an unequally-spaced OPA using the modified genetic algorithm, the grating lobes and side lobes can be well suppressed. Specifically, the PSLL of the far-field pattern reaches as low as 0.20 in 0° beam direction for a 2D 10×10 OPA with the inter-element spacing between 1 μm and 3 μm, which is much better than the traditional unequally-spaced OPA. The relationship between the optimized PSLL and the practical fabrication accuracy is also investigated. The results indicate that the proposed OPA can allow a certain fabrication deviation. Besides, the additional amplitude weighting method is applied to the optimized 2D unequally-spaced OPAs, and the simulation results show that the optimized unequally-spaced OPAs with amplitude weighting can achieve a better grating-lobe suppression. For the 2D 10×10 OPA, the PSLL can be further reduced to 0.18 in 0° beam direction. The proposed 2D low grating-lobe OPAs are expected to benefit many practical applications such as light detection and ranging, high-resolution display, and free-space optical communications.