Chip-based Brillouin lasers as spectral purifiers for photonic systems

TL;DR

This paper demonstrates the first chip-based Brillouin laser that offers high efficiency, single-line operation, and the lowest Schawlow-Townes frequency noise among chip lasers, serving as a spectral purifier for low-coherence sources.

Contribution

It introduces the first chip-based Brillouin laser with record-low frequency noise and spectral purification capabilities for compact laser systems.

Findings

Achieved high-efficiency, single-line operation in a chip-based Brillouin laser.

Recorded the smallest Schawlow-Townes frequency noise for a chip laser.

Enabled spectral purification of low-coherence laser sources.

Abstract

High coherence lasers are essential in a wide range of applications, however, such performance is normally associated with large laser cavities, because increasing energy storage reduces quantum phase noise and also renders the laser frequency less sensitive to cavity vibration. This basic scaling rule is at odds with an emerging set of optical systems that place focus on compact (optimally integrable) sources of high coherence light. These include phase-coherent optical communication using quadrature-amplitude-modulation, and also record-low phase noise microwave sources based upon optical comb techniques. In this work, the first, chip-based Brillouin laser is demonstrated. It features high-efficiency and single-line operation with the smallest recorded Schawlow-Townes frequency noise for any chip-based laser. Because the frequency offset between the laser's emission and the input pump is relatively small, the device provides a new function: spectral purification of compact, low coherence sources such as semiconductor lasers.