Atom-referenced on-chip soliton microcomb

TL;DR

This paper demonstrates an integrated, atom-referenced stabilized soliton microcomb system that achieves high frequency stability without the need for complex self-referencing techniques, suitable for portable high-precision spectroscopy.

Contribution

It introduces a fully stabilized microcomb generation method based on atomic references and injection-locking, eliminating the need for $f-2f$ techniques.

Findings

Achieved frequency stabilization of ~18 Hz at 1 second.

Demonstrated high-precision frequency determination with stability of 9.5×10⁻¹⁴.

Implemented a portable, integrated microcomb system for spectroscopy.

Abstract

For the applications of the frequency comb in microresonators, it is essential to obtain a fully frequency-stabilized microcomb laser source. Here, we demonstrate an atom-referenced stabilized soliton microcomb generation system based on the integrated microring resonator. The pump light around $1560.48\,\mathrm{nm}$ locked to an ultra-low-expansion (ULE) cavity, is frequency-doubled and referenced to the atomic transition of $^{87}\mathrm{Rb}$. The repetition rate of the soliton microcomb is injection-locked to an atomic-clock-stabilized radio frequency (RF) source, leading to mHz stabilization at $1$ seconds. As a result, all comb lines have been frequency-stabilized based on the atomic reference and could be determined with very high precision reaching $\sim18\,\mathrm{Hz}$ at 1 second, corresponding to the frequency stability of $9.5\times10^{-14}$. Our approach provides an integrated and fully stabilized microcomb experiment scheme with no requirement of $f-2f$ technique, which could be easily implemented and generalized to various photonic platforms, thus paving the way towards the portable and ultraprecise optical sources for high precision spectroscopy.