Development of a portable optical frequency standard with a small calcium cell

Calcium atoms could be trapped and locked directly in a small cell (about 20 cm long). A high power injection lock diode laser being frequency doubled to 422.5 nm by through a nonlinear crystal KNbO/sub 3/, is used to trap calcium atoms in the "heart" of the cell. The trapped atoms will be probed by a narrow linewidth extended-cavity diode laser. The diode laser then will be locked to the calcium /sup 3/P/sub 1/-/sup 1/S/sub 0/ intercombination line at 657 nm. The direct cell trapping and locking method makes it become possible to establish a compact high precision optical frequency standard.