, Volume 24, Issue 9, pp S903-S926

Beam parameters, mode structure and diffraction losses of slab lasers with unstable resonators

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Abstract

The properties of unstable resonators in on-axis and off-axis geometry were investigated both theoretically and experimentally. Diffraction loss, mode structure, beam quality and misalignment sensitivity were measured in single-shot operation with a gas-cooled Nd: YAG slab laser (4×12×100 mm3) and compared with theoretical results obtained by solving the Fresnel integral equation numerically. The excellent agreement allowed detailed resonator optimization. Furthermore, the resonator performance in high-power operation was investigated with two water-cooled Nd: YAG slab lasers (6×25×163 mm3 and 7×26×191 mm3) capable of 670 W of output power. Beam quality near the diffraction limit and a maximum output power of 475 W was achieved with an on-axis unstable resonator with variable-reflectivity mirror.