Low-Threshold Lasing in Colloidal InP/ZnSe/ZnS Quantum Dots via ZnSe Interlayer Engineering

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• Colloidal indium phosphide (InP) quantum dots (QDs) are heavy-metal-free alternatives for display technologies.
• Their potential for light amplification and use in lasers remains largely unexplored.

Purpose of the Study:

• To investigate light amplification and lasing in InP/ZnSe/ZnS core/multishell quantum dots.
• To understand the role of shell thickness and defect states on optical gain properties.

Main Methods:

• Fabrication of InP/ZnSe/ZnS core/multishell quantum dots with varying ZnSe interlayer thickness.
• Characterization using time-resolved spectroscopy to analyze carrier dynamics and Auger losses.
• Construction and testing of a liquid-state vertical-cavity surface-emitting laser (VCSEL).

Main Results:

• Achieved lasing in red-emitting InP QDs with high quantum yield.
• Demonstrated that optimal ZnSe interlayer thickness reduces amplified spontaneous emission thresholds.
• Identified defect states capturing hot carriers as a factor increasing losses and hindering population inversion.
• Observed lasing thresholds of 334 μJ/cm² (femtosecond) and 4.3 mJ/cm² (nanosecond) in the VCSEL.

Conclusions:

• InP-based QDs show significant potential as optical gain media for laser applications.
• Minimizing defects that capture hot carriers is essential for improving the lasing performance of InP QDs.