Dual-wavelength active optical clock

TL;DR

This paper reports the first experimental realization of a dual-wavelength active optical clock using cesium atoms, achieving ultra-narrow linewidths and proposing a cavity stabilization scheme to enhance frequency stability.

Contribution

It introduces the first dual-wavelength active optical clock with stabilized cavity length and demonstrates a method to improve frequency stability using a super-cavity locking scheme.

Findings

Detected dual-wavelength stimulated emission at 1359 nm and 1470 nm in Cs atoms.

Achieved a linewidth of 590 Hz for 1470 nm emission without cavity stabilization.

Proposed a cavity stabilization scheme to improve frequency stability by an order of magnitude.

Abstract

We experimentally realize the dual-wavelength active optical clock for the first time. As the Cs cell temperature is kept between 118 $^{\circ }C$ and 144 $^{\circ }C$, both the 1359 nm and the 1470 nm stimulated emission output of Cs four-level active optical clock are detected. The 1470 nm output linewidth of each experimental setup of Cs four-level active optical clock is measured to be 590 Hz with the main cavity length unstabilized. To stabilize the cavity length of active optical clock, the experimental scheme of 633 nm and 1359 nm good-bad cavity dual-wavelength active optical clock is proposed, where 633 nm and 1359 nm stimulated emission is working at good-cavity and bad-cavity regime respectively. The cavity length is stabilized by locking the 633 nm output frequency to a super-cavity with the Pound-Drever-Hall (PDH) technique. The frequency stability of 1359 nm bad-cavity stimulated emission output is then expected to be further improved by at least 1 order of magnitude than the 633 nm PDH system due to the suppressed cavity pulling effect of active optical clock, and the quantum limited linewidth of 1359 nm output is estimated to be 77.6 mHz.