An ultra-stable microresonator-based electro-optic dual frequency comb

TL;DR

This paper presents an ultra-stable, energy-efficient dual frequency comb source based on a lithium niobate microresonator, achieving extremely narrow linewidths without stabilization or post-processing, suitable for advanced spectroscopic applications.

Contribution

The authors demonstrate a novel lithium niobate microresonator device that generates ultra-stable dual combs with orthogonal polarizations and linewidths down to 400 microhertz, eliminating the need for stabilization.

Findings

Achieved relative linewidths down to 400 microhertz.

Generated dual combs with orthogonal polarizations.

Operates without stabilization or post-processing.

Abstract

Optical frequency combs emit narrow pulses of light with a stable repetition rate. Equivalently, the generated light spectrum consists of many discrete frequencies spaced by this same repetition rate. These precision light sources have become ubiquitous in applications of photonic technologies because they allow coherent sampling over a broad part of the optical spectrum. The addition of another comb, with a slightly different line spacing, results in a dual comb. Widely used in spectroscopy, dual combs allow one to read out the broad frequency response of a sample in a simple electronic measurement. Many dual comb applications require a high level of mutual coherence between the combs, but achieving this stability can be demanding. Here, by exploiting the rich structure of the nonlinear electro-optic tensor in lithium niobate, we generate ultra-stable dual combs with the two combs naturally having orthogonal polarizations. Our combs have relative linewidths down to 400 microhertz, and require no stabilization or post-processing methods. The ultra-high stability of the spectrum emitted by our device, along with its simplicity of operation and energy efficiency, offer a route to the deployment of robust and versatile dual comb sources.