Phase Control Of Coherent Diode Laser Arrays Using Liquid Crystals

The on-axis fields from separate elements of a coherent laser array can interfere either constructively or destructively, depending upon the relative phases. We describe thin film transistor (TFT) and direct-drive controlled arrays of liquid crystal phase shifters, which provide both phase matching and fine beamsteering. The transmissive liquid crystal devices contain homogeneously aligned layers of nematic liquid crystals sandwiched between two glass plates. The devices impart electrically controllable analog phase delays to laser beams passing through the cells. The devices are divided into arrays of individually controlled elements using separate transparent electrodes.