High-performance coherent population trapping atomic clock with direct-modulation distributed Bragg reflector laser

TL;DR

This paper presents a compact, high-performance CPT atomic clock using a directly modulated DFB laser, achieving excellent stability and simplifying the design for space applications.

Contribution

It introduces a novel CPT clock design with a directly modulated DFB laser, reducing size while maintaining high stability and performance.

Findings

Achieved a short-term frequency stability of 3.6 × 10^{-13} at 4 seconds.

Demonstrated a narrow linewidth and high contrast CPT signal.

Simplified the CPT clock configuration with a compact bichromatic light source.

Abstract

The coherent population trapping (CPT) atomic clock is very promising for use in next-generation spaceborne applications owing to its compactness and high performance. In this paper, we propose and implement a CPT atomic clock based on the direct modulation of a large-modulation-bandwidth and narrow-linewidth distributed Bragg reflector laser, which replaces the usually used external bulk modulator in the high-performance CPT clock. Our method retains the high performance while significantly reducing the size. Using this highly compact bichromatic light source and simplest CPT configuration, in which a circularly polarized bichromatic laser interrogates the ^{87}Rb atom system, a CPT signal of clock transition with a narrow linewidth and high contrast is observed. We then lock the local oscillator frequency to the CPT error signal and demonstrate a short-term frequency stability of 3.6 \times 10^{-13} {\tau}^{-1/2} (4 s \le {\tau} \le 200 s). We attribute it to the ultralow laser frequency and intensity noise as well as to the high-quality-factor CPT signal. This study can pave the way for the development of compact high-performance CPT clocks based on our scheme.