Active Faraday optical frequency standards

TL;DR

This paper introduces an active Faraday optical frequency standard based on cesium vapor, achieving a narrow linewidth of about 996 Hz and demonstrating potential for advanced optical atomic clocks.

Contribution

The work presents the first experimental demonstration of an active Faraday optical frequency standard with significantly narrowed linewidth and high stability, suitable for next-generation atomic clocks.

Findings

Linewidth reduced to approximately 996 Hz

Maximum emitted power of 75 μW achieved

Frequency stability surpasses natural linewidth by over 5000 times

Abstract

We propose the mechanism of active Faraday optical clock, and experimentally demonstrate active Faraday optical frequency standards based on 852 nm narrow bandwidth Faraday atomic filter by the method of velocity-selective optical pumping of cesium vapor. The center frequency of the active Faraday optical frequency standards is determined by the cesium 6 $^{2}S_{1/2}$ $F$ = 4 to 6 $^{2}P_{3/2}$ $F'$ = 4 and 5 crossover transition line. The optical heterodyne beat between two similar independent setups shows that the frequency linewidth reaches 996(26) Hz, which is 5.3 $\times$ 10$^{3}$ times smaller than the natural linewidth of the cesium 852 nm transition line. The maximum emitted light power reaches 75 $\upmu$W. The active Faraday optical frequency standards reported here have advantages of narrow linewidth and reduced cavity pulling, which can readily be extended to other atomic transition lines of alkali and alkaline-earth metal atoms trapped in optical lattices at magic wavelengths, making it useful for new generation of optical atomic clocks.