An Ultra-Stable Referenced Interrogation System in the Deep Ultraviolet for a Mercury Optical Lattice Clock

TL;DR

This paper presents the development of an ultra-stable deep ultraviolet light source, crucial for mercury optical lattice clocks, utilizing a highly stable Fabry-Pérot cavity and frequency stabilization techniques.

Contribution

The authors introduce a novel deep UV source with exceptional stability, achieved through a specialized cavity and frequency stabilization, tailored for mercury lattice clock applications.

Findings

Achieved fractional frequency stability at 1E-15 level.

Produced several milliwatts of 265.6 nm UV light.

Demonstrated system suitability for future mercury optical lattice clocks.

Abstract

We have developed an ultra-stable source in the deep ultraviolet, suitable to fulfill the interrogation requirements of a future fully-operational lattice clock based on neutral mercury. At the core of the system is a Fabry-P\'erot cavity which is highly impervious to temperature and vibrational perturbations. The mirror substrate is made of fused silica in order to exploit the comparatively low thermal noise limits associated with this material. By stabilizing the frequency of a 1062.6 nm Yb-doped fiber laser to the cavity, and including an additional link to LNE-SYRTE's fountain primary frequency standards via an optical frequency comb, we produce a signal which is both stable at the 1E-15 level in fractional terms and referenced to primary frequency standards. The signal is subsequently amplified and frequency-doubled twice to produce several milliwatts of interrogation signal at 265.6 nm in the deep ultraviolet.