32×32 Optical phased array with ultra-lightweight high-contrast-grating mirrors

Optical phased arrays (OPA) with fast response time are of great interest for various applications such as displays, free space optical communications, and laser radar. In this paper, we report on a novel 32×32 OPA with fast response time (<;4 microseconds), large field of view (±2°), and narrow beam divergence (0.1°). This is made possible by integrating ultra-lightweight high-contrast-grating (HCG) mirrors with high-speed electrostatic actuators in a dense two-dimensional array with high fill-factor. Consisting of a thin layer (400nm) of sub-wavelength polysilicon gratings, the HCG mirror has a high reflectivity (99.9%), a broad reflection bandwidth, and weighs only 140pg.