Compact sub-Hz Linewidth Laser Enabled by Self Injection Lock To a Sub-mL FP Cavity

TL;DR

This paper presents a compact, high-performance narrow linewidth laser achieved through self-injection locking to a miniature high-Q Fabry-Perot cavity, enabling stable, low-noise operation suitable for field deployment.

Contribution

The authors demonstrate a miniaturized, high-Q cavity-based narrow linewidth laser with simplified setup, surpassing commercial and on-chip solutions in linewidth and noise performance.

Findings

Linewidth of 60 mHz achieved

Integrated linewidth around 80 Hz

Exceeds performance of commercial NLLs

Abstract

Narrow linewidth laser(NLL) of high frequency stability and small form factor is essential to enable applications in long range sensing, quantum information and atomic clocks. Various high performance NLL have been demonstrated by Pound-Drever Hall(PDH) lock or self injection lock(SIL) of a seed laser to a vaccum-stabilized FP cavity of ultrahigh quality factor(Q). However they are often complicated lab setups due to the sophisticated stabilizing system and locking electronics. Here we report a compact NLL of 68mL volume, realized by SIL of a diode laser to a miniature FP cavity of 7.7x108 Q and 0.5mL volume, bypassing table-size vaccum, thermal and vibration isolation. We characterized the NLL with a self-delayed heterodyne system, the Lorentzian linewidth reaches 60mHz, and the integrated linewidth is ~80Hz. The frequency noise performance exceeds that of commercial NLLs and the best reported hybrid-integrated NLL realized by SIL to high Q on-chip ring resonators. Our work marks a major step toward a field-deployable NLL of superior performance utilizing ultra-high Q FP cavity.