Fourier transform detection of weak optical transitions with cyclic routines

TL;DR

This paper introduces a Fourier transform-based method for detecting weak optical transitions in cold atoms with high sensitivity, enabling detection with fewer atoms and applying it to ytterbium clock transitions.

Contribution

The paper presents a novel Fourier transform detection technique that enhances sensitivity for weak optical transitions in cold atoms, outperforming conventional methods.

Findings

Achieved ~20 times sensitivity enhancement over traditional scanning methods.

Detected clock lines with fewer than 1000 atoms in a magneto-optical trap.

Measured the ac-Stark shift of the ytterbium clock transition.

Abstract

We demonstrate a means of detecting weak optical transitions in cold atoms that undergo cyclic routines with high sensitivity. The gain in sensitivity is made by probing atoms on alternate cycles leading to a regular modulation of the ground state atom population when at the resonance frequency. The atomic transition is identified by conducting a fast Fourier transform via algorithm or instrument. We find an enhancement of detection sensitivity compared to more conventional scanning methods of $\sim 20$ for the same sampling time, and can detect clock lines with fewer than $10^3$ atoms in a magneto-optical trap. We apply the method to the $(6s^{2})$ $ ^{1}S_{0} - (6s6p)$ $^{3}P_{0}$ clock transition in $^{171}$Yb and $^{173}$Yb. The ac-Stark shift of this line in $^{171}$Yb is measured to be 0.19(3) kHz$\cdot$W$^{-1}\cdot$m$^2$ at 556 nm.