Mid-infrared InAs/InP quantum-dot lasers.

Mid-infrared semiconductor lasers operating in the 2.0-5.0 μm spectral range play an important role for various applications, including trace-gas detection, biomedical analysis, and free-space optical communication. InP-based quantum-well (QW) and quantum-dash (Qdash) lasers are promising alternatives to conventional GaSb-based QW lasers because of their lower cost and mature fabrication infrastructure. However, they suffer from high threshold current density (Jth) and limited operation temperatures. InAs/InP quantum-dot (QD) lasers theoretically offer lower Jth owing to their three-dimensional carrier confinement. Nevertheless, achieving high-density, uniform InAs/InP QDs with sufficient gain for lasing over 2 μm remains a major challenge. Here, we report the first demonstration of mid-infrared InAs/InP QD lasers emitting beyond 2 μm. Five-stack InAs/In0.532Ga0.468As/InP QDs grown by molecular-beam epitaxy exhibit room-temperature photoluminescence at 2.04 μm. Edge-emitting lasers achieve lasing at 2.018 μm with a low Jth of 589 A cm-2 and a maximum operation temperature of 50 °C. Notably, the Jth per layer (118 A cm-2) is the lowest ever reported for room-temperature InP-based mid-infrared lasers, outperforming QW/Qdash counterparts. These results pave the way for a new class of low-cost, high-performance mid-infrared light sources using InAs/InP QDs, marking a notable step forward in the development of mid-infrared semiconductor lasers.