Shot-noise-limited laser power stabilization for the AEI 10 m Prototype interferometer.

The AEI 10 m Prototype interferometer is an experiment to investigate the standard quantum limit of interferometry and, in particular, its relevance in gravitational-wave detection. As such it has stringent requirements on the power stability of its high-power light source. In this Letter we present the power stabilization concept of the 35 W Nd:YAG laser system used in the AEI 10 m Prototype. With a shot-noise-limited multiphotodetector sensing scheme we achieved a relative power noise level of 1.8×10^-9  Hz^-1/2 in a frequency band of 100 Hz to 1 kHz. The limiting noise sources at lower and higher frequencies are analyzed, and possible improvements on the power noise sensing are discussed.