Continuous-wave, single-frequency 229 nm laser source for laser cooling of cadmium atoms

TL;DR

This paper reports a continuous-wave 229 nm laser source for laser cooling of cadmium atoms, achieved through harmonic generation, with successful magneto-optical trapping of all stable isotopes, including those relevant for optical lattice clocks.

Contribution

It demonstrates a high-power, single-frequency 229 nm laser source using harmonic generation and applies it to trap all stable cadmium isotopes, advancing laser cooling techniques.

Findings

Achieved 0.56 W output at 229 nm with >34% conversion efficiency.

Successfully trapped all stable cadmium isotopes including $^{111}$Cd and $^{113}$Cd.

Demonstrated potential for optical lattice clock applications.

Abstract

Continuous-wave output at 229 nm for the application of laser cooling of Cd atoms was generated by the 4th harmonic using two successive second harmonic generation stages. Employing a single-frequency optically pumped semiconductor laser as a fundamental source, 0.56 W of output at 229 nm was observed with a 10-mm long, Brewster-cut BBO crystal in an external cavity with 1.62 W of 458 nm input. Conversion efficiency from 458 nm to 229 nm was more than 34%. By applying a tapered amplifier as a fundamental source, we demonstrated magneto-optical trapping of all stable Cd isotopes including isotopes $^{111}$Cd and $^{113}$Cd, which are applicable to optical lattice clocks.