Abstract

Frequency stabilization of lasers using an external reference has been studied for many years and is by now a very advanced topic. A widely used technique utilizes optical cavities as the external reference, but since the late 1990’ies a technique using spectral hole burning in rare-earth-metal-doped crystals has also proven useful for reducing the laser frequency line width (see e.g. reference 1). Both these techniques employ the Pound-Drever-Hall method of phase- modulating the laser beam going to the external reference, and in this way the phase of the laser output is compared to the phase coherence of the reference.

© 2007 IEEE