Coherent beam addition of GaAlAs lasers by binary phase gratings

A general technique for combining laser beams coherently using binary gratings has been developed. Experiments were performed with lasers from a monolithic linear GaAlAs array. The grating transmittance profile was designed to convert the light beams from the array into a single beam with high efficiency. Optical feedback through the grating locked the lasers together in proper relative phase. The far-field diffraction pattern of the sum was practically identical in shape to that of a single laser. Coupling efficiencies greater than 80% appear to be feasible with this technique. The method is applicable to a variety of laser systems (gas, solid state, etc.) and is readily extendable to a two-dimensional array of lasers.