Colloidal Quantum Dot Infrared Lasers Featuring Sub-Single-Exciton Threshold and Very High Gain

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• Infrared laser devices traditionally require high pumping intensities and suffer from short gain lifetimes.
• Colloidal quantum dots (CQDs) show promise as gain media but face challenges with Auger recombination and low gain coefficients.

Purpose of the Study:

• To develop efficient infrared gain media using engineered CQDs.
• To reduce optical gain thresholds and improve lasing performance in the near-infrared spectrum.

Main Methods:

• Utilized PbS/PbSSe core/alloyed-shell CQDs as the gain medium.
• Investigated Auger recombination suppression and amplified spontaneous emission (ASE) thresholds.
• Employed transient absorption spectroscopy to measure optical gain and exciton populations.
• Achieved near-infrared lasing at 1670 nm.

Main Results:

• Achieved suppressed Auger recombination with a lifetime of 485 ps.
• Lowered the ASE threshold to 300 µJ cm⁻², with a net modal gain coefficient of 2180 cm⁻¹.
• Demonstrated a reduced optical gain threshold of 0.45 excitons-per-dot due to ground state absorption bleaching.
• Attained a fivefold reduction in ASE threshold (0.70 excitons-per-dot) and near-infrared lasing at 1670 nm (0.87 excitons-per-dot threshold).

Conclusions:

• Engineered core/shell CQDs significantly reduce infrared lasing thresholds, comparable to visible counterparts.
• This advancement enables solution-processed infrared laser diodes.
• Highlights the potential of CQDs for next-generation optoelectronic devices.