Optical materials: Semiconducting nanocrystals light up the way

A new type of nanocrystal that can be used as a laser material is reported in Nature magazine. 'Soft' optical materials like this can easily be processed in solution, offering flexibility for laser design, and the devices may find use in applications including lab-on-a-chip technologies and quantum information processing devices.
Semiconductor nanocrystals have excellent light-emitting properties, making them good candidates for use in laser applications. But achieving the crucial condition for lasing — optical amplification — has proved problematic: normally the nanocrystals need to contain at least two excitons (electron–hole pairs, which are the precursors for light emission in semiconductors), but owing to the nanocrystal’s tiny size, the excitons annihilate each other before optical amplification can occur.
Victor I. Klimov and colleagues circumvent this problem by designing nanocrystals with cores and shells made from different semiconductor materials, in such a way that electrons and holes are physically isolated from each other. In such engineered nanocrystals, only one exciton per nanocrystal is required for optical amplification, as has here been experimentally demonstrated by Klimov and colleagues. This opens the door to practical use in laser applications.
CONTACT
Victor I. Klimov (Los Alamos National Laboratory, NM, USA)
Tel: +1 505 665 8284; E-mail: klimov@lanl.gov

Todd D. Krauss (University of Rochester, NY, USA) N&V author
Tel: +1 585 275 5093; E-mail: krauss@chem.rochester.edu