Stimulated Emission and Lasing through Bulk Nanocrystals

Pieter Geiregat^a^,^b, Ivo Tanghe^a^,^b^,^c, Margarita Samoli^a, Servet Ataber Cayan^a^,^b, Kai Chen^d^,^e, Justin Hodgkiss^d, Isabella Wagner^d, Iwan Moreels^a, Dries Vanthourhout^b^,^c, Zeger Hens^a^,^b

^aPhysics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Ghent, Belgium

^bNoLIMITS Center for Non-Linear Microscopy and Spectroscopy, Belgium, Ghent University, Gante, Belgium

^cPhotonics Research Group, Ghent University, Belgium, Technologiepark-Zwijnaarde, 126, Gent, Belgium

^dSchool of Chemical and Physical Sciences, Victoria University of Wellington, Wellington, New Zealand, PO Box 600, Wellington, New Zealand

^eRobinson Research Institute, Victoria University of Wellington, Wellington, New Zealand, PO Box 600, Wellington, New Zealand

Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS23 & Sustainable Technology Forum València (STECH23) (MATSUS23)

#NCFun23 - Fundamental Processes in Nanocrystals and 2D Materials

VALÈNCIA, Spain, 2023 March 6th - 10th

Organizers: Valerio Pinchetti and Shalini Singh

Invited Speaker, Pieter Geiregat, presentation 282
DOI: https://doi.org/10.29363/nanoge.matsus.2023.282
Publication date: 22nd December 2022

Nanostructured semiconductors, or quantum dots (QDs), are heavily investigated for their applications in light emission such as light emitting diodes and lasers. The premise of cost-effective solution processing of such devices based on nanocrystals has recently driven research towards electrically pumped population inversion in laser diode structures. Challenges however remain to achieve net light amplification in the cavity due to a balance between limited material gains and lossy electrical contacts. Further reductions in threshold current densities, mainly limited by the non-radiative cap of ca. 1 nanosecond on the gain lifetime, are also required to achieve stable operation. Finally, color tunability is limited to the red by the gain bandwidth of the red-emitting CdSe/CdS QDs or even core/shell nanoplatelets used.
Here, we show that weakly confined charge carriers in giant CdS quantum dots display disruptive optical gain metrics that could alleviate these remaining issues. Being active in the green part of the spectrum, their properties match and even outcompeting state-of-the-art colloidal materials in the red. Material gain coefficients up to 50.000 cm^-1 combined with a broad gain window of 160 nm are found. Also, a very promising gain lifetime close to 3 ns is found. Invoking a model of stimulated emission based on bulk semiconductor physics, we are able to explain all of these remarkable gain metrics, yet only if a large band gap renormalization effect is invoked. Based on these unique materials, we demonstrate amplified spontaneous emission and lasing action under nanosecond optical excitation. Our results show that weakly confined nanomaterials are excellent gain materials, combining straightforward wet chemical synthesis and the promise of solution processability with beyond state-of-the-art gain metrics.

Acknowledgements:

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