Two-step pulse observation for Raman-Ramsey coherent population trapping atomic clocks

TL;DR

This paper introduces a two-step pulse observation technique for Raman-Ramsey CPT atomic clocks, improving frequency stability by reducing light sensitivity and enhancing signal-to-noise ratio through a novel low-intensity resonance scheme.

Contribution

It presents a new two-step pulse observation method that combines Raman-Ramsey scheme with low light intensity to improve atomic clock stability and signal quality.

Findings

Resonance characteristics were accurately modeled using density matrix analysis.

Experimental measurements confirmed the theoretical predictions.

The method reduces frequency sensitivity to light intensity while maintaining high SNR.

Abstract

We propose a two-step pulse observation method to enhance frequency stability for coherent population trapping (CPT) atomic clocks. The proposed method is a Raman-Ramsey scheme with low light intensity at resonance observation, and provides a Ramsey-CPT resonance with both reduced frequency sensitivity to the light intensity and a high signal-to-noise ratio by reducing the repumping into a steady dark state. The resonance characteristics were calculated based on density matrix analysis of a $\Lambda$-type three level system that was modeled on the $^{133}$Cs-D$_1$ line, and the characteristics were also measured using a vertical-cavity surface-emitting laser and a Cs vapor cell.