Grating-lobe-suppressed optical phased array with optimized element distribution

A grating-lobe-suppressed 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 one-dimensional (1-D) and two-dimensional (2-D) 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 0.1 and 0.23 in 0° beam direction for a 1-D 20-element OPA and a 2-D 10 × 10 OPA, respectively, which is much better than the traditional unequally-spaced OPA. The relationship between the optimized PSLL and the practical fabrication accuracy is investigated. The results indicate that the proposed OPA can allow a certain fabrication deviation, and the PSLL can keep a low level within the whole scanning range of 180°, although a slightly higher PSLL is achieved for a larger beam angle. Besides, the simulations results also show that, the spacing range between adjacent elements and the element number should be appropriately chosen to achieve a better side-lobe-suppression and a narrow beam width.