Laser power stabilization using optical ac coupling and its quantum and technical limits

Abstract

We demonstrate an active power stabilization of a Nd:YAG laser employing the optical ac-coupling scheme and derive its fundamental quantum limit. This limit is 3dB better than the one encountered in traditional power stabilization schemes. In our experiment, the optical ac coupling improved the shotnoise-limited sensitivity of the stabilization photodetector by a factor of 11.2. With an independent photodetector, we measured a relative power stability of 3:7 × 10-9 Hz-1/2 at frequencies of around 200kHz. A detailed investigation of the performance limit of our experiment revealed a novel noise source that disturbed the fundamental mode field in the optical resonator. This effect could be of relevance to many precision experiments using optical resonators. © 2009 Optical Society of America.