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

Abstract

We propose and demonstrate a 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 ≈20 spontaneously emitted photons per molecule, limited by the interaction time, while using a bandpass filter to suppress detected scattered laser light by ∼10^{6}. This general technique represents a powerful tool for high-fidelity fluorescence detection of molecules and is particularly well suited to molecular laser cooling and trapping experiments.