Sub-20 kHz low frequency noise near ultraviolet miniature external cavity laser diode

TL;DR

This paper introduces a compact, single-mode, near-UV laser diode with ultra-low frequency noise below 20 kHz, high side-mode suppression, and customizable fiber Bragg grating properties, suitable for quantum and metrology applications.

Contribution

The work demonstrates a novel, compact, and customizable FBG-based laser diode operating below 400 nm with ultra-low frequency noise and high spectral purity.

Findings

Intrinsic linewidth of 14 kHz in the near-UV range

Side-mode suppression ratio up to 40 dB

Milliwatt-level output power

Abstract

We present a compact InGaN fiber Bragg grating (FBG) semiconductor laser diode operating below 400 nm in the single-mode emission regime. This compact coherent laser source exhibits an intrinsic linewidth of 14 kHz in the near-UV range and a side-mode suppression ratio reaching up to 40 dB accompanied by a mW-level output power. Furthermore, the properties of the FBG, including its central wavelength, bandwidth, and reflectivity, can be readily customized to fulfill specific requirements. As a result, the small footprint design of this laser is compatible with integration into a standard butterfly package to ease the lab-to-market technology transfer. The combination of low frequency noise and fibered output signal positions these FBG laser systems as strong candidates for hybridization with integrated photonic platforms tailored for quantum information processing and metrology.