FUNDAMENTAL MODE DETERMINATION FOR GUARANTEEING DIFFRACTION-LIMITED BEAM QUALITY OF LASERS WITH HIGH-OUTPUT POWERS

Fundamental mode operation of lasers can be guaranteed by applying a c ombination of a pin hole with a second suitable aperture (fundamental mode determinator: FMD) in an adapted resonator. Especially high power solid state lasers can operate with high efficiencies in TEM00-mode u sing the FMD to overcome the problems of widely used resonator designs . Large mode volumes can be realized and the overall potential of any active material for fundamental mode emission can be determined. As an example a Nd:YAG laser with a mode diameter of 7.3 mm in a 9.5 mm rod was realized. 34 W average output power of diffraction limited radiat ion with 1.1% slope efficiency could be observed with a conventional N d:YAG laser. The FMD is especially useful for resonators with phase co njugating mirror (PCM). 31 W average power of TEM00 were obtained from such a laser with PCM based on stimulated Brillouin scattering. (C) 1 998 Published by Elsevier Science B.V.