An all-sapphire Cs gas cell for a chip-scale atomic clock

Abstract

We realized a Cs gas cell for a chip-scale atomic clock fabricated from single-crystal sapphire chips, which have extremely-low gas penetration coefficients. The coherent population trapping (CPT) resonance spectrum was evaluated to validate the developed sapphire Cs gas cell. A CPT resonance with a contrast of 1.5%, a frequency shift (from the Cs hyperfine transition frequency) of 55.9 kHz, and a full width at half maximum of 2.2 kHz was obtained at an incident light intensity of 40 μW cm−2. The frequency shift was mainly caused by the collision between Ne sealed in the gas cell and Cs atoms. From the experimental results, the pressure of Ne was estimated to be 10.7 kPa.