Coherence assisted resonance with sub-lifetime-limited linewidth

TL;DR

This paper introduces a new method to achieve resonance linewidths below the coherence lifetime limit by using cross-correlation of laser intensity modulations, with potential applications in spectroscopy and sensing.

Contribution

The authors demonstrate a novel technique that reduces resonance linewidths below the coherence lifetime limit using coherence-assisted resonance with laser modulation correlation.

Findings

Achieved linewidths of 1/30 of the lifetime-limited width in experiments.

Experimental results align with analytical and numerical models.

Technique is easily implementable and broadly applicable.

Abstract

We demonstrate a novel approach to obtain resonance linewidth below that limited by coherence lifetime. Cross correlation between induced intensity modulation of two lasers coupling the target resonance exhibits a narrow spectrum. 1/30 of the lifetime-limited width was achieved in a proof-of-principle experiment where two ground states are the target resonance levels. Attainable linewidth is only limited by laser shot noise in principle. Experimental results agree with an intuitive analytical model and numerical calculations qualitatively. This technique can be easily implemented and should be applicable to many atomic, molecular and solid state spin systems for spectroscopy, metrology and resonance based sensing and imaging.