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.

Bonding formation and gas absorption using Au/Pt/Ti layers for vacuum packaging

“…While the thickness of the Ti layer was set at 40 nm, Pt layers of 2.5 and 5 nm thickness were deposited on the Ti layer to investigate their diffusion barrier ability. In a previous study 5 , the degassing step by vacuum annealing (at 200 °C for 10 min) efficiently removed the absorbed water molecules; thus, the packaged cesium gas cell was successfully achieved. The Pt/Ti layers were degassed under the same conditions, as shown in Fig.…”

Simple and low-temperature vacuum packaging process by using Au/Ta/Ti metal multilayer

“…A number of researchers have developed a non-evaporative getter (NEG) to remove the residual gas in the package. [8][9][10][11][12][13][14][15][16] NEG films installed in the package, which serve as chemical pumps, can be activated by thermal treatment. This method has been generally used in MEMS device fabrications.…”