Extended Short-Wave Infrared Colloidal Quantum Dot Lasers with Nanosecond Excitation.

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• Solution-processed gain media offer scalable, integrable laser solutions.
• Current technology covers visible to short-wave infrared (SWIR) wavelengths (<1650 nm).
• Extended SWIR (1600-2500 nm) is crucial for LIDAR, imaging, and monitoring but lacks scalable materials.

Purpose of the Study:

• To demonstrate optical gain in the extended SWIR using PbS colloidal quantum dots (CQDs).
• To achieve lasing in the 2150-2500 nm range using CQD-based distributed feedback cavities.
• To investigate the impact of CQD size on optical gain thresholds and explore nanosecond excitation.

Main Methods:

• Fabrication of PbS CQDs with varying sizes.
• Integration of CQDs into distributed feedback laser cavities.
• Optical gain and lasing measurements under nanosecond pulsed excitation.
• Transient absorption spectroscopy for gain threshold modeling.

Main Results:

• Demonstrated optical gain in the extended SWIR (1600-2500 nm) using PbS CQDs.
• Achieved tunable lasing between 2150 nm and 2500 nm.
• Larger CQDs reduced the optical gain threshold by a factor of 36, reaching an amplified spontaneous emission (ASE) threshold of 42 µJ cm⁻².
• First demonstration of gain and lasing under nanosecond excitation from PbS CQDs.

Conclusions:

• PbS CQDs provide a scalable solution for extended SWIR lasers.
• CQD size tuning is critical for reducing gain thresholds.
• This work enables compact, practical CQD infrared lasers and potential for electrically driven laser diodes.