A small calcium beam optical frequency standard with fully-sealed vacuum tube

In this paper a small Calcium beam optical frequency standard utilizing fully-sealed Calcium beam vacuum tube owning smaller size compared with vacuum system with flanges is demonstrated. Adopting the electron shelving detection method, we detect the clock transition 657 nm saturation absorbing spectroscopy whose linewidth is 500 kHz. The instability of this small optical frequency standard is 6.8×10
^-14
at 1 second and 1.8×10
^-15
after 1000 seconds of averaging by comparing with another small Calcium beam optical frequency standard whose reported instability is 3.0×10
^-14
at 1 second. The optical part of the whole system is specially designed for robustness and miniaturization.