# Realization of phase locking in good-bad-cavity active optical clock

## TL;DR

This paper demonstrates phase locking in dual-wavelength active optical clocks, significantly reducing cavity-pulling effects and linewidth, by experimentally stabilizing cavity lengths with high precision using phase locking of independent lasers.

## Contribution

First experimental realization of cavity-length stabilization in dual-wavelength active optical clocks using phase locking of independent lasers.

## Key findings

- Frequency tracking accuracy better than 3×10^{-16} at 1 s
- Linewidth of 1470 nm bad-cavity laser reduced to 53 Hz
- Suppression of asynchronous cavity-length variation effects

## Abstract

The residual cavity-pulling effect limits further narrowing of linewidth in dual-wavelength (DW) good-bad-cavity active optical clocks (AOCs). In this paper, we for the first time experimentally realize the cavity-length stabilization of the 1064/1470 nm DW-AOCs by utilizing the phase locking technique of two independent 1064 nm good-cavity lasers. The frequency tracking accuracy between the two main-cavities of DW-AOCs is better than $3 \times {10^{ - 16}}$ at 1 s, and can reach $1 \times {10^{ - 17}}$ at 1000 s. Each 1470 nm bad-cavity laser achieves a most probable linewidth of 53 Hz, which is about a quarter of that without phase locking. The influence of the asynchronous cavity-lengths variation between two DW laser systems is suppressed.