arXiv:2004.01752 · Optics Letters
Double-heterodyne probing for an ultra-stable laser based on spectral hole burning in a rare-earth-doped crystal
Nicolas Galland, Nemanja Lučić, S. Zhang, Héctor Álvarez Martínez, Rodolphe Le Targat, Alban Ferrier, Philippe Goldner, Bess Fang, Signe Louise Seidelin, Yann Le Coq
Abstract
We present an experimental technique for realizing a specific absorption spectral pattern in a rare-earth-doped crystal at cryogenic temperatures. This pattern is subsequently probed on two spectral channels simultaneously, thereby producing an error signal allowing frequency locking of a laser on the said spectral pattern. Appropriate combination of the two channels leads to a substantial reduction in detection noise, paving the way to realizing an ultra-stable laser for which the detection noise can be made arbitrarily low when using multiple channels. We use this technique to realize a laser with a frequency instability of 1.7 × 1 0 − 15 at 1 s, not limited by the detection noise but by environmental perturbation of the crystal. This is comparable with the lowest instability demonstrated at 1 s to date for rare-earth-doped crystal stabilized lasers.