Interferometric gravitational wave detectors require high optical power, single frequency lasers with very good beam quality and high amplitude and frequency stability as well as high long-term reliability as input light source. For GEO 600 a laser system with these properties is realized by a stable planar, longitudinally pumped 12 W Nd:YAG rod laser which is injection-locked to a monolithic 800 mW Nd:YAG non-planar ring oscillator. Frequency control signals from the mode cleaners are fed to the actuators of the non-planar ring oscillator which determines the frequency stability of the system. The system power stabilization acts on the slave laser pump diodes which have the largest influence on the output power. In order to gain more output power, a combined Nd:YAG-Nd:YVO 4 system is scaled to more than 22 W.

Experiments on a high-power end-pumped Nd:YAG rod laser with an efficient birefringence compensation will be presented. A linearly polarized output power of 114 W with an M 2 -value of 1.05 was realized. Furthermore, the from our best knowledge highest injection-locked singlefrequency output power of 87 W in a nearly diffraction-limited beam was demonstrated.

Experiments on a high-power Nd:YAG rod laser with an output power up to 97 W for the next generation of interferometric gravitational wave detectors will be presented. Furthermore, the highest injection-locked single-frequency output power of 87 W in a linearly polarized, diffraction-limited beam was demonstrated.

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