Green Light from Red-Emitting Nanocrystals: Broadband, Low-Threshold Lasing from Colloidal Quantum Shells in Optical...

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• Semiconductor nanoplatelets, or quantum shells (QSs), show promise for lasers due to suppressed Auger recombination and long multiexciton lifetimes.
• Achieving tunable multiexciton lasing with QSs in photonic cavities remains a challenge.

Purpose of the Study:

• To demonstrate broadly tunable lasing from QS films using nanopillar arrays.
• To investigate the role of multiexciton transitions in achieving tunable laser emission.
• To explore the potential of QSs for next-generation colloidal nanocrystal lasers.

Main Methods:

• Fabrication of close-packed CdS/CdSe/CdS QS films on Si nanopillar arrays.
• Characterization of stimulated emission and spectral tuning across single, biexciton, and multiple exciton transitions.
• Analysis of gain threshold and cavity fluence threshold in relation to Auger suppression.
• Modeling of lasing emission tuning by varying array period while maintaining optical quality.

Main Results:

• Broadly tunable lasing achieved from QS films, with emission wavelengths spanning from single exciton (∼634 nm) to multiple excitons (∼615-565 nm).
• Low ensemble-averaged gain threshold ( ∼ 2.6) and photonic cavity fluence threshold (∼4 μJ/cm²) attributed to effective Auger recombination suppression.
• Lasing emission tuning correlated with model predictions based on nanopillar array period adjustments.
• Preservation of mode confinement and quality (Q) factors during spectral tuning.

Conclusions:

• Demonstrated a viable approach for achieving broadly tunable lasing from colloidal nanocrystal systems.
• Highlighted the significance of Auger suppression in QSs for low-threshold, tunable laser operation.
• Paved the way for the development of advanced colloidal nanocrystal lasers with tailored optical properties.