APPLIED PHYSICS: Tunable Nanocrystalline Lasers

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Science  28 Jun 2002:
Vol. 296, Issue 5577, pp. 2299b
DOI: 10.1126/science.296.5577.2299b

The discrete energy levels of quantum dots, or nanocrystals, provide a potential advantage for their use in laser sources requiring thermal stability and low threshold. Moreover, as the energy spacing is dependent on the size of the nanocrystal, the emitted wavelength can be tuned by size selection. However, although optical gain has been observed in colloidal nanocrystalline thin films, the intrinsic disorder of the colloids and the dominance of nonradiative recombination mechanisms have prevented lasing from occurring and have limited operation to cryogenic temperatures.

Eisler et al. show that by spin coating a layer of CdSe nanocrystals dispersed in titania onto a patterned diffraction grating, and selecting the layer thickness to match the Bragg condition of the grating, lasing can be achieved at room temperature. The ease of processing and the ready availability of other semiconductors in nanocrystalline format may allow the development of laser sources over a wide range of wavelengths and on a variety of substrates. — ISO

Appl. Phys. Lett. 80, 4614 (2002).

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