LOSSLESS SIDELOBE SUPPRESSION FOR A PHASE-LOCKED CO//2 WAVEGUIDE ARRAY.

Recently, phase-coupled arrays of semiconductor and gas lasers have been developed. The far-field pattern of spatially distinct lasers contains grating sidelobes which significantly reduce the available power in the central lobe. A spatial filtering technique, called coherent aperture filling by amplitude-to-phase conversion, is described for channeling the majority of the sidelobe energy into the central lobe. The technique was tested on a phase-locked CO//2 ridged waveguide array. Highly efficient sidelobe suppression results from a lossless field transformation that converts amplitude nonuniformity to phase nonuniformity. The resultant aperture-filled array has a nearly uniform amplitude distribution. An additional phase nonuniformity giving an output with nearly uniform amplitude and phase. The field transformation is accomplished by an afocal imaging system.