Fundamental mode determination for guaranteeing diffraction limited beam quality of lasers with high output powers

Abstract

Fundamental mode operation of lasers can be guaranteed by applying a combination 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 TEM 00-mode using 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 radiation with 1.1% slope efficiency could be observed with a conventional Nd:YAG laser. The FMD is especially useful for resonators with phase conjugating mirror (PCM). 31 W average power of TEM 00 were obtained from such a laser with PCM based on stimulated Brillouin scattering.