High-spectral-purity laser system for the AURIGA detector optical readout

We describe a low-frequency-noise laser system conceived for the readout of small mechanical vibrations. The system consists of a Nd:YAG source stabilized to a high-finesse Fabry-Perot cavity and achieves the best performance in the range 1-10 kHz with a minimum residual noise of 4 x 10(-3) Hz/rootHz. We perform an extended characterization of the frequency stability by means of an independent optical cavity and we also measure the residual fluctuations after transmission through an optical fiber. Our apparatus is optimized for use in an optical readout for the gravitational wave detector AURIGA, where a laser system with the characteristics reported here will allow an improvement of one order of magnitude in the detector sensitivity. (C) 2003 Optical Society of America.