Velocity-selective direct frequency-comb spectroscopy of atomic vapors

TL;DR

This paper investigates velocity-selective two-photon spectroscopy of rubidium atoms using optical frequency combs with different repetition rates, combining experimental results and theoretical modeling to understand the effects on atomic transition excitation.

Contribution

It introduces a combined experimental and theoretical approach to analyze how repetition rate influences velocity-selective two-photon transitions in rubidium vapor using frequency combs.

Findings

Repetition rate significantly affects the excitation spectra.

Experimental spectra align well with the theoretical model.

Different comb repetition rates produce distinguishable velocity selectivity patterns.

Abstract

We present an experimental and theoretical investigation of two-photon direct frequency-comb spectroscopy performed through velocity-selective excitation. In particular, we explore the effect of repetition rate on the $\textrm{5S}_{1/2}\rightarrow \textrm{5D}_{3/2, 5/2}$ two-photon transitions excited in a rubidium atomic vapor cell. The transitions occur via step-wise excitation through the $\textrm{5P}_{1/2, 3/2}$ states by use of the direct output of an optical frequency comb. Experiments were performed with two different frequency combs, one with a repetition rate of $\approx 925$ MHz and one with a repetition rate of $\approx 250$ MHz. The experimental spectra are compared to each other and to a theoretical model.