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Red, green and blue lasing enabled by single-exciton gain in colloidal quantum dot films


Colloidal quantum dots exhibit efficient photoluminescence with widely tunable bandgaps as a result of quantum confinement effects1. Such quantum dots are emerging as an appealing complement to epitaxial semiconductor laser materials, which are ubiquitous and technologically mature, but unable to cover the full visible spectrum (red, green and blue; RGB)2. However, the requirement for high colloidal-quantum-dot packing density, and losses due to non-radiative multiexcitonic Auger recombination, have hindered the development of lasers based on colloidal quantum dots3,4,5,6,7,8,9. Here, we engineer CdSe/ZnCdS core/shell colloidal quantum dots with aromatic ligands, which form densely packed films exhibiting optical gain across the visible spectrum with less than one exciton per colloidal quantum dot on average. This single-exciton gain allows the films to reach the threshold of amplified spontaneous emission at very low optical pump energy densities of 90 µJ cm–2, more than one order of magnitude better than previously reported values9,10,11,12. We leverage the low-threshold gain of these nanocomposite films to produce the first colloidal-quantum-dot vertical-cavity surface-emitting lasers (CQD-VCSEL). Our results represent a significant step towards full-colour single-material lasers.

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Figure 1: Structural characteristics of CQDs and their spin-cast closely packed films.
Figure 2: Edge emission in a stripe excitation geometry over a range of pumping levels.
Figure 3: Dynamics of CQD light emission from epitaxial-like thin films under various excitation conditions.
Figure 4: Optically pumped CQD-VCSELs in the red and green.


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The authors thank G. Lei, J. Tang and T. Grimsley for their help in CQD film characterization, K. Roh for subnanosecond pumped ASE, and H. Maris, R. Zia, C. Dodson, D. Pacifici and I. Ozden for fruitful discussions. Research was funded by the Department of Energy (BES office), the Air Force Office for Scientific Research and the National Science Foundation.

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Authors and Affiliations



C.D. designed the research, performed the experiments and analysed the results. J.L. performed the green CQD-VCSEL and analysed the results. C.B. and J.S.S. synthesized the nanocrystal CQDs. S.C-S. participated in analysis of the results. A.N. contributed to all aspects of the work. C.D., J.L. and A.N. co-wrote the manuscript.

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Correspondence to Arto Nurmikko.

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Competing interests

C.B., J.S. and S.C-S. are stockholders of QD Vision Inc., which sells light-emitting products comprising quantum dots.

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Dang, C., Lee, J., Breen, C. et al. Red, green and blue lasing enabled by single-exciton gain in colloidal quantum dot films. Nature Nanotech 7, 335–339 (2012).

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