Advanced Liquid Crystal on Silicon Optical Phased Arrays

Steven Serati, Jay Stockley

Proceedings, IEEE Aerospace Conference (2002)


Non-mechanical beamsteering eliminates the need for massive optomechanical components to steer the field of view of optical systems. This benefit is to come in the form of compact, low-power, light-weight optical phased arrays (OPAs) that provide better control with greater flexibility in their steering capability than their mechanical counterparts. Due to such benefits, there is a need to develop technologies that provide this capability without greatly sacrificing other parameters such as aperture size, efficiency, and scanning range. One technology being explored for OPA implementation is liquid crystal on silicon (LCoS). The LCoS technology provides a means for manufacturing high resolution backplanes using high-volume semiconductor processes commonly used for very large scale integrated (VLSI) circuits. VLSI production minimizes the cost of backplane fabrication and allows integration of electronic circuits into the backplane structure to provide individual addressing of each pixel while minimizing interconnects to the OPA. Since each pixel is individually addressed, the phase modulation is not restricted to phase ramps but provides any type of phase profile. This capability is useful for dynamic correction of phase distortions across the aperture due to heating effects, for example. Also, it allows the reset period to be randomized to minimize sidelobe amplitudes. However, VLSI technology has its own set of limitations that have slowed the development of high-speed, high-resolution, non-mechanical beamsteerers having good optical efficiency and a large scanning range. This paper discusses the benefits and limitations of the LCoS approach and methods for improving the state-of-the-art.

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