Quantum dot lasers tolerate extreme feedback
Researchers demonstrate telecom-grade quantum dot lasers can operate near coherence collapse without isolators, paving the way for simpler, cost-effective photonic integrated circuits.
Researchers at King Abdullah University of Science and Technology (KAUST) and the University of California, Santa Barbara have demonstrated that quantum dot (QD) lasers can maintain telecom-grade performance even under extreme optical feedback, eliminating the need for isolators in PICs.
Using a custom experimental platform that delivers continuous feedback up to 0 dB, the team directly measured the coherence collapse threshold of QD Fabry–Perot lasers at −6.7 dB (21.4% return).
Despite operating near this limit, the lasers supported 10 Gbps external modulation, stable operation between 15–45 °C, and over 100 hours of continuous feedback operation with excellent device-to-device reproducibility.
The findings, published in Light: Science & Applications, were reinforced by theoretical modelling based on the Lang–Kobayashi analysis, which confirmed that scale PIC cavities further enhance QD feedback tolerance.
Compared to quantum well, quantum wire, and VCSEL platforms, the QD Fabry–Perot devices showed superior stability under feedback.
By removing the need for optical isolators, this work simplifies PIC packaging, improves manufacturability, and reduces system costs.
It also provides clear design rules for integrating QD lasers into next-generation PIC systems for communications, sensing, LiDAR, and large-scale photonic platforms.
This research underscores the potential of QD lasers to enable energy-efficient, reliable, and cost-effective PICs, accelerating their adoption in high-performance optical technologies.
