New concepts and results in laser power stabilization

In the recent decade the development of highpower, high-sensitivity photodetectors and low-noise sensing techniques lead to achievable relative power stabilities at the level of 10^-9 Hz^-1/2 for frequencies between about 10 Hz and 10 kHz. A new power stabilization concept involving the novel optical ac coupling technique complements these high-sensitivity photodetectors. This technique improves the sensitivity of a photodetector by about one order of magnitude. Furthermore, it beats the quantum limit of traditional power stabilization concepts and opens a whole new range of attainable power stabilities that seemed to have been inaccessible due to technical limitations before. In this article we review various laser power stabilization experiments in the field of ground-based gravitational wave detectors, present the best results and discuss their limits.