CONTINUOUSLY VARIABLE OPTICAL BEAM SPLITTER

A continuously adjustable optical beam splitter includes a circular to linear polarization converter, a polarization rotator, and a polarization beam splitter that apportions light between two outputs. The polarization converter can include a quarter wave plate. The polarization rotator can include a mechanically rotated half wave plate or an electronically controlled liquid crystal variable retarder. The light source can be astronomical, reflected LIDAR light, or a laser beam from a remote laser communication node. Also disclosed is a free space laser communication terminal that implements the disclosed optical beam splitter, wherein the optical beam splitter diverts substantially all received laser light to an alignment channel during initial alignment, and then during message communication diverts more than 90%, and in embodiments up to 98%, of the received light to a communication channel, while alignment is maintained by continuing to divert the remaining laser light to the alignment channel.