Electronic sideband locking of 318.6nm UV laser to an ultrastable optical cavity with a wide continuously tunable range

TL;DR

This paper presents a novel electronic sideband locking technique for a 318.6 nm UV laser system, enabling wide continuous tuning while maintaining frequency stability, which is valuable for precision atomic spectroscopy.

Contribution

The work introduces a method to lock and tune a UV laser over 4 GHz using electronic sideband locking, enhancing flexibility and stability for atomic experiments.

Findings

Achieved continuous 4 GHz tuning of UV laser

Maintained laser lock during tuning process

Potential for improved precision in atomic spectroscopy

Abstract

We have demonstrated a frequency-stabilized tunable 318.6 nm ultraviolet (UV) laser system for the single-photon 6S1/2 - nP (n = 70 ~ 100) Rydberg excitation of cesium atoms. The 637.2 nm laser produced by single-pass sum frequency generation from two infrared fiber lasers is offset locked to a high-finesse ultra-low expansion (ULE) optical cavity placed in ultra-high vacuum using the electronic sideband locking technique. The generated 318.6 nm UV laser via cavity-enhanced second-harmonic generation can be continuously tuned over 4 GHz by indirectly changing modulation frequency on the electro-optic phase modulator while the whole laser system remains locked. We analyze the tuning range mainly depends on the modulator bandwidth and the tunable range of the seed laser. The locking scheme offers a method to compensate the frequency difference between the reference frequency and the goal frequency to a desired excited state, and has huge potential in precision spectroscopic experiments of cold atoms.