Beam-Pointing Stabilization and Ladar Heterodyne Mixing Efficiency Increase Using a Liquid Crystal Phased Array Device

Abstract

Laser radar imaging systems often require the ability to accurately point the transmitted laser beam as well as the ability to mix the return light with a single mode receiver. An addressable liquid crystal phased array provides the precise spatially dependent phase shifts needed to achieve such beam stability and increased ladar heterodyne mixing efficiency. The device consists of a layer of nematic liquid crystals sandwiched between two substrates. One substrate is uniformly grounded, while the other is etched with narrow, closely spaced individual 1-D electrodes. The liquid crystals underneath a given electrode are rotated by applying an appropriate voltage, thus generating a birefringent phase delay. Two of these writable one-dimensional gratings can be cascaded to implement two dimensional phase profiles.