Laser beam combiner: applications to space-borne laser communications.

An attractive source for spaceborne laser communications is the directly modulated single-mode GaAs/GaAlAs injection laser. GaAlAs lasers, however, show low power per diode and wide beam divergence. A simple optical concept for a laser beam combiner overcomes diode laser limitations: an array of closely packed parallel collimated laser beams can be handled in an optical system as a single beam. Diffractive spreading causes all bundle beams to overlap in the far field, producing incoherent power addition with 50% power throughput and good far-field performance.