Dual-microcavity narrow-linewidth Brillouin laser

TL;DR

This paper presents a dual-microcavity laser system that achieves ultralow noise and tunability, suitable for precision applications, by combining stimulated Brillouin scattering and frequency stabilization on a chip.

Contribution

It introduces a novel dual-microcavity configuration that significantly reduces frequency noise and enables terahertz tunability in a chip-integrable laser system.

Findings

Fractional frequency noise reduced to 7.8×10⁻¹⁴ at 10 Hz offset

Achieved terahertz tunability in a microresonator-based laser

Demonstrated optical spectroscopy with hertz-level resolution

Abstract

Ultralow noise, yet tunable lasers are a revolutionary tool in precision spectroscopy, displacement measurements at the standard quantum limit, and the development of advanced optical atomic clocks. Further applications include LIDAR, coherent communications, frequency synthesis, and precision sensors of strain, motion, and temperature. While all applications benefit from lower frequency noise, many also require a laser that is robust and compact. Here, we introduce a dual-microcavity laser that leverages one chip-integrable silica microresonator to generate tunable 1550 nm laser light via stimulated Brillouin scattering (SBS) and a second microresonator for frequency stabilization of the SBS light. This configuration reduces the fractional frequency noise to $7.8\times10^{-14} 1/\sqrt{Hz}$ at 10 Hz offset, which is a new regime of noise performance for a microresonator-based laser. Our system also features terahertz tunability and the potential for chip-level integration. We demonstrate the utility of our dual-microcavity laser by performing optical spectroscopy with hertz-level resolution.