Characterization of Cs vapor cell coated with octadecyltrichlorosilane using coherent population trapping spectroscopy

TL;DR

This study demonstrates the use of coherent population trapping spectroscopy to characterize a Cs vapor cell coated with octadecyltrichlorosilane, revealing detailed resonance features, lifetimes, and potential for atomic clock applications.

Contribution

First detailed CPT-based characterization of an OTS-coated Cs vapor cell, including resonance structure, adsorption energy, and coherence lifetimes, for atomic clock development.

Findings

Narrow resonance linewidth observed at the top of Doppler-broadened structure

Cs-OTS adsorption energy measured at 0.42 eV

Hyperfine population lifetime T1 of 1.6 ms and coherence lifetime T2 of 0.5 ms

Abstract

We report the realization and characterization using coherent population trapping (CPT) spectroscopy of an octadecyltrichlorosilane (OTS)-coated centimeter-scale Cs vapor cell. The dual-structure of the resonance lineshape, with presence of a narrow structure line at the top of a Doppler-broadened structure, is clearly observed. The linewidth of the narrow resonance is compared to the linewidth of an evacuated Cs cell and of a buffer gas Cs cell of similar size. The Cs-OTS adsorption energy is measured to be (0.42 $\pm$ 0.03) eV, leading to a clock frequency shift rate of $2.7\times10^{-9}/$K in fractional unit. A hyperfine population lifetime, $T_1$, and a microwave coherence lifetime, $T_2$, of 1.6 and 0.5 ms are reported, corresponding to about 37 and 12 useful bounces, respectively. Atomic-motion induced Ramsey narrowing of dark resonances is observed in Cs-OTS cells by reducing the optical beam diameter. Ramsey CPT fringes are detected using a pulsed CPT interrogation scheme. Potential applications of the Cs-OTS cell to the development of a vapor cell atomic clock are discussed.