In isolator-free photonic integrated circuits, quantum dot lasers show superior feedback tolerance when benchmarked against quantum well, quantum wire, and VCSEL platforms.

The work provides practical design rules for isolator-free integration, potentially reducing packaging complexity, manufacturing challenges, and system costs across communications, sensing, LiDAR, and large-scale photonic systems.

Theoretical modeling based on Lang–Kobayashi analysis suggests the coherence collapse boundary shifts toward 0 dB in centimeter-scale PIC cavities, increasing tolerance under practical conditions.

The study demonstrates stable telecom-grade performance near the coherence collapse boundary, maintaining 10 Gbps external modulation and operation across a wide temperature range from 15 to 45 degrees Celsius.

Experimentally, coherence collapse was observed in a quantum dot laser at −6.7 dB, marking the first measurement of this threshold for the quantum dot platform.

By clarifying the true feedback limit of quantum dot lasers in realistic PIC environments, the findings address a major obstacle to scalable, energy-efficient optical systems.

The platform employs optimized quantum dot epitaxial growth and a semiconductor optical amplifier to compensate for signal loss, enabling robust operation under realistic feedback.

Led by Prof. Yating Wan at KAUST in collaboration with UC Santa Barbara, the research defines the feedback limits of quantum dot lasers to enable isolator-free photonic integrated circuits.