SPATIAL CHARACTERISTICS OF A LASER-OSCILLATOR FORMED BY OPTICALLY-WRITTEN HOLOGRAPHIC GAIN-GRATING

We investigate the spatial characteristics of a Nd: YAG unidirectional ring resonator formed by an adaptive holographic gain-grating. Diffra ction-limited spatial output is demonstrated from the resonator even w ith very strong intracavity phase distortion. We also show that, despi te good intracavity phase compensation and good spatial output quality , the output mode size is not generally the same as the self-intersect ing input beam that forms the gain hologram. A simplified theory, to a ccount approximately for a spatially-Gaussian input beam, gives qualit ative agreement with the key features observed in the experimental res onator.