Novel external resonators for high power diode lasers with improved beam quality

Summary form only given. Current commercially available high power diode lasers lack beam quality, i.e. they have limited possibility of small foci in combination with long Rayleigh lengths. We improve beam quality with the help of newly designed external resonators. It is well known, that external resonators can drastically improve beam quality of conventional gain-guided broad area lasers. The technique of Petersen (1998) makes use of self induced phase conjugation with the help of a photorefractive crystal. We present a design which dispenses with the crystal and phase conjugation and therefore becomes considerably simpler and cheaper.