Narrow Linewidth near-UV InGaN Laser Diode based on External Cavity Fiber Bragg Grating

TL;DR

This paper reports the development of a narrow linewidth near-UV InGaN laser diode with high coherence, achieved through external cavity fiber Bragg grating technology, suitable for applications requiring high interferometric resolution.

Contribution

It introduces a novel fiber Bragg grating design enabling single-mode, single-frequency operation of a near-UV laser diode with ultra-narrow linewidth and high side-mode suppression.

Findings

44 dB side-mode suppression ratio

sub-MHz integrated linewidth

16 kHz intrinsic linewidth

Abstract

We realize a fiber Bragg grating InGaN based laser diode emitting at 400 nm and demonstrate its high coherency. Thanks to the fabrication of a narrow band fiber Bragg grating in the near-UV, we can reach single-mode and single-frequency regimes for the self-injection locked diode. The device exhibits 44 dB side-mode-suppression-ratio and mW output power. Detailed frequency noise analysis reveals sub-MHz integrated linewidth and 16 kHz intrinsic linewidth. Such a narrow linewidth laser diode in the near-UV domain with a compact and low-cost design could find applications whenever coherency and interferometric resolutions are needed.