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C&E News, Nano Letters Highlight Quantum Dot Lasing Work by Chemistry Staff

Important quantum dot lasing advances by the Nanotechnology and Advanced Spectroscopy Team were recently published in Nano Letters (Nano Lett., DOI: 10.1021/nl103801e) and highlighted by C&E News (Jan. 17th, 2011, v.89, n.3). Practical quantum dot lasing could open the door to new and important applications in optics.

The Nanotechnology Team published proof-of-principle experiments on lasing in cadmium selenide quantum dots (CdSe) in 2000 (Science, v. 290, p. 314, 2000), but due to material property limitations, sustained nanocrystal lasing has remained elusive. The main problem has been a very fast decay of optical gain due to a process called Auger recombination that restricts the ability of photons to escape the material, which in turn limited lasing. In the intervening years, the team discovered that coating a cadmium selenide quantum dot core with a relatively thick monolayer of cadmium sulfide (CdS) suppresses the Auger recombination enough to make lasing practical. The Nano Letter article describes their approach to using CdSe/CdS core-shell nanocrystals with a think outer shell. The Team’s research also shows the importance of interfacial effects in Auger recombination. Specifically, by applying so-called fluorescence line narrowing measurements they observed that the lengthening of Auger lifetimes directly correlates with the formation of the interfacial CdSeS alloy layer, which "smoothes" the nanocrystal confinement potential.

This significant advance in Auger-suppression strategies should greatly simplify applications of nanocrystals in practical lasing technologies.

February 2011

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