Coherent Population Trapping Resonances in Buffer Gas-filled Cs Vapor Cells with Push-Pull Optical Pumping

TL;DR

This paper combines theoretical analysis and experimental methods to study coherent population trapping resonances in buffer gas-filled Cs vapor cells using push-pull optical pumping, highlighting high contrast and potential for atomic clock applications.

Contribution

It introduces a detailed analysis of push-pull optical pumping in CPT resonances and demonstrates high-contrast resonances in Cs vapor cells, advancing atomic clock technology.

Findings

Achieved 78% CPT resonance contrast in a cm-scale cell.

Analyzed the impact of laser intensity on key CPT parameters.

Discussed the potential of PPOP for high-performance atomic clocks.

Abstract

We report on a theoretical study and experimental characterization of coherent population trapping (CPT) resonances in buffer gas-filled vapor cells with push-pull optical pumping (PPOP) on Cs D1 line. We point out that the push-pull interaction scheme is identical to the so-called lin per lin polarization scheme. Expressions of the relevant dark states, as well as of absorption, are reported. The experimental setup is based on the combination of a distributed feedback (DFB) diode laser, a pigtailed intensity Mach-Zehnder electro-optic modulator (MZ EOM) for optical sidebands generation and a Michelson-like interferometer. A microwave technique to stabilize the transfer function operating point of the MZ EOM is implemented for proper operation. A CPT resonance contrast as high as 78% is reported in a cm-scale cell for the magnetic-field insensitive clock transition. The impact of the laser intensity on the CPT clock signal key parameters (linewidth - contrast - linewidth/contrast ratio) is reported for three different cells with various dimensions and buffer gas contents. The potential of the PPOP technique for the development of high-performance atomic vapor cell clocks is discussed.