Velocity-comb modulation transfer spectroscopy

TL;DR

This paper introduces velocity-comb modulation transfer spectroscopy, a novel technique leveraging multi-frequency comb lasers to improve atomic utilization and frequency stability in laser spectroscopy, advancing optical clock technology.

Contribution

It proposes a new MTS method using velocity-selective resonance of comb lasers to enhance atomic utilization and frequency stability in sub-Doppler spectroscopy.

Findings

Frequency stability improved by nearly a factor of 3 compared to single-frequency lasers.

Preliminary results confirm theoretical predictions of enhanced spectral amplitude.

Method has potential for significant breakthroughs in optical clock stability.

Abstract

Sub-Doppler laser spectroscopy is a crucial technique for laser frequency stabilization, playing a significant role in atomic physics, precision measurement, and quantum communication. However, recent efforts to improve frequency stability appear to have reached a bottleneck, as they primarily focus on external technical approaches while neglecting the fundamental issue of low atomic utilization (< 1%), caused by only near-zero transverse velocity atoms involved in the transition. Here, we propose a velocity-comb modulation transfer spectroscopy (MTS) solution that takes advantage of the velocity-selective resonance effect of multi-frequency comb lasers to enhance the utilization of non-zero-velocity atoms. In the probe-pump configuration, each pair of counter-propagating lasers interacts with atoms from different transverse velocity-comb groups, independently contributing to the spectral amplitude and signal-to-noise ratio. Preliminary proof-of-principle results show that the frequency stability of the triple-frequency laser is optimized by nearly a factor of \sqrt{3} compared to the single-frequency laser, consistent with theoretical expectations. With more frequency comb components, MTS-stabilized lasers are expected to achieve order-of-magnitude breakthroughs in frequency stability, taking an important step toward next-generation compact optical clocks. This unique method can also be widely applied to any quantum system with a wide velocity distribution, inspiring innovative advances in numerous fields with a fresh perspective.