Cavity ring-down spectroscopy for the detection of atomic beams

Abstract

We present our results on the development of a technique for the detection of dilute atomic beams by cavity ring-down spectroscopy (CRDS). These measurements were realized with an external cavity diode laser targeting the erbium 400.9 nm transition and a customized ring-down cavity under vacuum. Collimated atomic beams of different number densities were generated by controlling the temperature of a tantalum foil micro-crucible. Absorption values between 3×10-6 and 7×10^-6 were measured with a precision on the order of 10^-6. Number densities of erbium atoms were inferred to be between 2 – 4 × 10⁶ cm^-3. This work demonstrates for the first time the capability of studying dilute atomic beams of refractory materials with high accuracy utilizing CRDS. The proposed approach can be extended to the measurement of other refractory elements, such as the actinides.