Hertz-linewidth semiconductor lasers using CMOS-ready ultra-high-$Q$ microresonators

TL;DR

This paper demonstrates CMOS-compatible microresonators with record high Q factors enabling ultra-coherent, low-noise integrated semiconductor lasers and microcombs, advancing scalable manufacturing of coherent optical systems.

Contribution

It introduces CMOS-foundry-fabricated microresonators with record high Q, achieving ultra-low noise in integrated lasers and microcombs, bridging lab performance with scalable production.

Findings

Record high Q factor over 260 million achieved

Five orders-of-magnitude noise reduction demonstrated

Fundamental noise below 1 Hz$^2$ Hz$^{-1}$ in an integrated laser

Abstract

Driven by narrow-linewidth bench-top lasers, coherent optical systems spanning optical communications, metrology and sensing provide unrivalled performance. To transfer these capabilities from the laboratory to the real world, a key missing ingredient is a mass-produced integrated laser with superior coherence. Here, we bridge conventional semiconductor lasers and coherent optical systems using CMOS-foundry-fabricated microresonators with record high $Q$ factor over 260 million and finesse over 42,000. Five orders-of-magnitude noise reduction in the pump laser is demonstrated, and for the first time, fundamental noise below 1 Hz$^2$ Hz$^{-1}$ is achieved in an electrically-pumped integrated laser. Moreover, the same configuration is shown to relieve dispersion requirements for microcomb generation that have handicapped certain nonlinear platforms. The simultaneous realization of record-high $Q$ factor, highly coherent lasers and frequency combs using foundry-based technologies paves the way for volume manufacturing of a wide range of coherent optical systems.