Resonance Raman optical cycling for high-fidelity fluorescence detection of molecules

TL;DR

This paper introduces a resonance Raman optical cycling technique that enables high-fidelity fluorescence detection of molecules by manipulating their emission properties, significantly improving signal clarity in high-background environments.

Contribution

The authors develop and demonstrate a novel method combining Raman scattering and optical cycling for efficient fluorescence detection of molecules with diagonal Franck-Condon factors.

Findings

Achieved approximately 20 spontaneously emitted photons per molecule.

Suppressed scattered laser light by a factor of about 10^6.

Effective for high-precision molecular fluorescence detection in various settings.

Abstract

We propose and demonstrate a novel technique that combines Raman scattering and optical cycling in molecules with diagonal Franck-Condon factors. This resonance Raman optical cycling manipulates molecules to behave like efficient fluorophores with discrete absorption and emission profiles that are readily separated for sensitive fluorescence detection in high background light environments. Using a molecular beam of our test species, SrF, we realize up to an average of $\approx20$ spontaneously emitted photons per molecule, limited by the interaction time, while using a bandpass filter to suppress detected scattered laser light by $\sim10^{6}$. This general technique represents a powerful tool for high-fidelity fluorescence detection of molecules in any setting and is particularly well-suited to molecular laser cooling and trapping experiments.