Hyperfine spectroscopy using co-propagating pump-probe beams

TL;DR

This paper demonstrates a co-propagating pump-probe technique for hyperfine spectroscopy that offers advantages like no crossover resonances, Doppler-free signals, and improved signal-to-noise ratio, enabling precise hyperfine interval measurements.

Contribution

The paper introduces and validates a co-propagating pump-probe method for hyperfine spectroscopy, highlighting its advantages over traditional counter-propagating techniques.

Findings

No crossover resonances observed.

Higher signal-to-noise ratio achieved.

Precise hyperfine interval measurements performed.

Abstract

We have shown earlier that hyperfine spectroscopy in a vapor cell using co-propagating pump-probe beams has many advantages over the usual technique of saturated-absorption spectroscopy using counter-propagating beams. The main advantages are the absence of crossover resonances, the appearance of the signal on a flat (Doppler-free) background, and the higher signal-to-noise ratio of the primary peaks. Interaction with non-zero-velocity atoms causes additional peaks, but only one of them appears within the primary spectrum. We first illustrate the advantages of this technique for high-resolution spectroscopy by studying the $D_2$ line of Rb. We then use an acousto-optic modulator (AOM) for frequency calibration to make precise hyperfine-interval measurements in the first excited $P_{3/2}$ state of $^{85,87}$Rb and $^{133}$Cs.