Inverted crossover resonance aiding laser cooling of $^{171}$Yb

TL;DR

This paper reports the observation of an inverted crossover resonance in $^{171}$Yb, which enhances laser cooling efficiency and enables precise spectroscopy, resulting in colder atomic temperatures and improved frequency measurements.

Contribution

It introduces the observation of an inverted crossover resonance in $^{171}$Yb and demonstrates its application in laser cooling and high-precision spectroscopy.

Findings

Achieved atomic cooling to 20 μK using the resonance.

Used the resonance for laser frequency stabilization.

Measured isotopic shifts and hyperfine separations.

Abstract

We observe an inverted crossover resonance in $\pi$-driven four-level systems, where $F'-F=0,+1$. The signal is observed through saturated absorption spectroscopy of the $(6s^{2})$ $^{1}S_{0}$ $-$ $(6s6p)$ $^{3}P_{1}$ transition in $^{171}$Yb, where the nuclear spin $I=1/2$. The enhanced absorption signal is used to generate a dispersive curve for 556 nm laser frequency stabilisation and the stabilised light cools $^{171}$Yb atoms in a two-stage magneto-optical trap, achieving temperatures of 20 $\mu$K. The Doppler-free spectroscopy scheme is further used to measure isotopic frequency shifts and hyperfine separations for the intercombination line in ytterbium.