No abstract

The best plano-convex quartz crystals resonators can have quality factors up to a few billion at low temperature, which makes them interesting for ultrastable clocks. For this application, it's best they are optomechanically actuated. The first step towards this is to demonstrate they can be used as optical Fabry-Perot cavities with almost no change to their typical piezoelectric building. This paper is focused on the feasability of such optical use.

Data on the refractive index of silver thin films are scarce in the literature, and largely dependent on both the deposition method and thickness. We measure the refractive index of silver films at cryogenic temperature with a technique that takes advantage of the absorption of the films and the corresponding peculiar properties of Fabry–Perot cavities: a frequency shift between the reflection and transmission peaks, together with a modified cavity bandwidth. We demonstrate a decrease in the real value of the refractive index, together with a decrease in its imaginary value at 4 K.