Hybrid integrated ultra-low linewidth coil stabilized isolator-free widely tunable external cavity laser

TL;DR

This paper presents a hybrid-integrated external cavity laser with record-low linewidth and wide tunability, stabilized without an optical isolator, suitable for scalable quantum and sensing applications.

Contribution

It introduces a fully integrated, ultra-low linewidth, widely tunable laser stabilized to an integrated coil-resonator without using an optical isolator.

Findings

Achieved 3-7 Hz linewidth across 60 nm tuning range.

Demonstrated 27-60 Hz integral linewidth with 1.8E-13 Allan deviation.

Stabilization without optical isolator using resilience to optical feedback.

Abstract

Precision applications including quantum computing and sensing, mmWave/RF generation, and metrology, demand widely tunable, ultra-low phase noise lasers. Today, these experiments employ table-scale systems with bulk-optics and isolators to achieve requisite noise, stability, and tunability. Photonic integration will enable scalable, reliable and portable solutions. Here we report a hybrid-integrated external cavity widely tunable laser stabilized to a 10-meter-long integrated coil-resonator, achieving record-low 3 - 7 Hz fundamental linewidth across a 60 nm tuning range and 27 - 60 Hz integral linewidth with 1.8E-13 Allan deviation at 6.4 ms across 40 nm, delivering orders of magnitude frequency noise and integral linewidth reduction over state of the art. Stabilization is achieved without an optical isolator, leveraging resilience to optical feedback of 30 dB beyond that of commercial DFB lasers. The laser and reference cavity are fabricated in the same Si3N4 CMOS-compatible process, unlocking a path towards fully integrated visible to ShortWave-IR frequency stabilized lasers.