Quantum dots have ideal chemistry

17 Jun 2002

US researchers have observed optical gain and stimulated emission at room temperature in chemically-synthesized nanocrystal quantum dots. Based on II-VI materials, the development could lead to a new class of nanoscopic solid-state lasers.
The emission frequency of the CdSe dots can be continuously tuned according to their size. In contrast, emission wavelengths in epitaxially grown quantum dots are controlled by the growth material's composition..
This is because the nanocrystal dots are smaller than epitaxial dots - between 2 and 8 nm compared with more than 10 nm..
Using colloidal chemistry rather than epitaxial growth, Victor Klimov and colleagues at the Los Alamos National Laboratory and the Massachusetts Institute of Technology made films containing the semiconductor nanoparticles. This method permits the straightforward manufacture of dense quantum-dot arrays..
Crucial to the breakthrough was the realization that the density of quantum dots in the films had to be sufficiently high to produce stimulated emission..
Previous efforts had relied on dilute concentrations of nanocrystals. In these films stimulated emission cannot compete with losses due to non-radiative decay..
Klimov says that the method makes colloidal quantum dots ideal starting materials for the assembly of optical devices..

Story courtesy of Opto and Laser Europe magazine.