Continuous-wave laser source at the 148 nm nuclear transition of Th-229

TL;DR

This paper reports a continuous-wave 148 nm laser source using second-harmonic generation in strontium tetraborate, aimed at exciting the 229Th nuclear isomeric state with potential for high spectral density.

Contribution

It introduces a novel CW laser at 148 nm based on nonlinear frequency conversion for nuclear excitation applications.

Findings

Achieved 1.3 nW of VUV power at 148 nm

Demonstrated stable second-harmonic generation in SrB4O7

Paves the way for resonant nuclear excitation experiments

Abstract

A continuous-wave laser source at 148.4 nm based on second-harmonic generation in randomly quasi-phase matched strontium tetraborate, SrB4O7, is demonstrated. It provides (1.3-0.6+0.7) nW of VUV power in a single pass for an incident UV laser power of 325 mW. The laser system is developed for the resonant laser excitation of the 229Th nucleus to its low-energy isomeric state. For a frequency-stabilized laser system we expect to reach similar VUV power spectral densities as in previous pulsed laser excitation experiments of the nuclear transition in 229Th-doped crystals.