Narrow Linewidth Distributed Feedback Lasers Utilizing Distributed Phase Shift

TL;DR

This paper introduces a novel DFB laser design with a distributed phase shift that enhances single-mode stability, reduces linewidth, and improves efficiency, verified through modeling and experimental validation.

Contribution

It presents an optimized DFB laser structure with a distributed phase shift, achieving broader stable operation and significantly narrower linewidths compared to traditional designs.

Findings

Achieved stable single-mode operation over a broader current range.

Reduced optical linewidth from 1.3 MHz to 220 kHz.

Improved power efficiency and side mode suppression ratio.

Abstract

This study proposes and experimentally demonstrates a distributed feedback (DFB) laser with a distributed phase shift (DPS) region at the center of the DFB cavity. By modeling the field intensity distribution in the cavity and the output spectrum, the DPS region length and phase shift values have been optimized. Experimental comparisons with lasers using traditional {\pi}-phase shifts confirm that DFB lasers with optimized DPS lengths and larger phase shifts (up to 15{\pi}) achieve stable single longitudinal mode operation over a broader current range, with lower threshold current, higher power slope efficiency, and a higher side mode suppression ratio (SMSR). Furthermore, the minimum optical linewidth is reduced significantly, from 1.3 MHz to 220 kHz.