Performance evaluation of a liquid-crystal-on-silicon spatial light modulator

D optical phased array antennas formed by a liquid crystal on silicon (LCOS) spatial light modulator are described for free-space laser communication and high-resolution wavefront control. The device consists of an 2-D array of 10243768 phase modulator elements, each with controlled voltage, and can induce a phase shift from 0 to 2p for wavelengths up to the near IR. When the device is used as a wavefront corrector, 18.7 waves peak-valley (at 632.8 nm) of aberration in the op- tical system is corrected to a residual of 1/9 wave peak-valley, or 1/30 wave rms. The Strehl ratio improved from 0.006 to 0.83 after correction. An additional linear phase ramp was added to the correction phase ramp to simultaneously correct and steer the laser beam. Continuous steering over 64 mrad in the X-Y plane with a steering accuracy higher than 10 mrad has been obtained. The 1-D beam-steering efficiency is 80% at the maximum steering angle of 4 mrad. These results suggest that an LCOS device can be used to achieve very high-resolution wavefront control at very high efficiency. © 2004 Society of Photo-Optical Instrumentation Engineers.