Mode Control and Dynamic Population Gratings in Quantum-Dot Lasers

TL;DR

This paper demonstrates that quantum-dot lasers can achieve stable, single-mode operation using a simple cavity design with dynamic population gratings, enabling scalable, tunable, and feedback-resistant on-chip light sources.

Contribution

It introduces a novel cavity design leveraging dynamic population gratings in quantum-dot lasers for stable single-mode lasing without complex fabrication.

Findings

Achieved 46 dB side-mode suppression ratio (SMSR) in single-ring lasers.

Demonstrated > 46 nm tuning range with dual-ring Vernier lasers.

Supported 32 Gbps data transmission with feedback resilience.

Abstract

Single-mode operation is essential for integrated semiconductor lasers, yet most solutions rely on regrowth, etched gratings, or other complex fabrication steps that limit scalability. We show that quantum-dot (QD) lasers can achieve stable single-mode lasing through a simple cavity design using dynamic population gratings (DPGs). Owing to the low lateral carrier diffusion of QDs, a strong standing-wave-induced carrier grating forms in a reverse-biased saturable absorber and provides self-aligned, mode-selective feedback not attainable in quantum-well devices. A single-ring laser achieves 46 dB side-mode suppression ratio (SMSR), while a dual-ring Vernier laser delivers ($>$ 46 nm) tuning range and up to 52.6 dB SMSR, with continuous-wave operation up to $80\,^{\circ}\mathrm{C}$. The laser remains single-mode under $-10.6$ dB external optical feedback and supports isolator-free data transmission at 32 Gbps. These results establish DPG-enabled QD lasers as a simple and scalable route to tunable, feedback-resilient on-chip light sources for communication, sensing, and reconfigurable photonic systems.