Tunable VUV Frequency Comb for $^{\mathrm{229m}}$Th Nuclear Spectroscopy

TL;DR

This paper introduces a tunable vacuum-ultraviolet frequency comb based on cavity-enhanced seventh-harmonic generation, designed to facilitate laser spectroscopy of the $^{229m}$Th nuclear clock transition, aiding future nuclear-based optical clock development.

Contribution

The work presents the first tunable VUV frequency comb covering the $^{229m}$Th nuclear transition range, enabling precise spectroscopy for nuclear clock research.

Findings

Achieved broad spectral coverage in the VUV range

Successfully tuned the comb to match the $^{229m}$Th transition uncertainty

Demonstrated cavity-enhanced seventh-harmonic generation technique

Abstract

Laser spectroscopy of the $^{\mathrm{229m}}$Th nuclear clock transition is necessary for the future construction of a nuclear-based optical clock. Precision laser sources with broad spectral coverage in the vacuum ultraviolet are needed for this task. Here, we present a tunable vacuum-ultraviolet frequency comb based on cavity-enhanced seventh-harmonic generation. Its tunable spectrum covers the current uncertainty range of the $^{\mathrm{229m}}$Th nuclear clock transition.