First-order thermal insensitivity of the frequency of a narrow spectral hole in a crystal

• DOI: 10.1103/physreva.107.013518
• Publication Date: 2023-01-23T15:02:24Z
• Authors: S. Zhang; S. Seidelin; R. Le Targat; P. Goldner; B. Fang; Y. Le Coq
• Keywords: [PHYS]Physics [physics]; 0301 basic medicine; 03 medical and health sciences; FOS: Physical sciences; [PHYS] Physics [physics]; Physics - Optics; Optics (physics.optics)

The possibility of generating an narrow spectral hole in a rare-earth doped crystal opens the gateway to a variety of applications, one of which is the realization of an ultrastable laser. As this is achieved by locking in a pre-stabilized laser to the narrow hole, a prerequisite is the elimination of frequency fluctuations of the spectral hole. One potential source of such fluctuations can arise from temperature instabilities. However, when the crystal is surrounded by a buffer gas subject to the same temperature as the crystal, the effect of temperature-induced pressure changes may be used to counterbalance the direct effect of temperature fluctuations. For a particular pressure, it is indeed possible to identify a temperature for which the spectral hole resonant frequency is independent of the first-order thermal fluctuations. Here, we measure frequency shifts as a function of temperature for different values of the pressure of the surrounding buffer gas, and identify the ``magic'' environment within which the spectral hole is largely insensitive to temperature.<br/>6 pages, 5 figures<br/>