Demonstration of a nanoparticle-based optical diode

D. Alexander et al, "Demonstration of a nanoparticle-based optical diode", Optics Lett. 31, 1957(2006)

This is a neat demonstration of an optical diode (light transmission only in one direction, using a pair of CdSe/ZnS core-shell nanocrystals with the appropriate fluorescence and absorption spectra. The diode "switching speed" is limited to about 25-33 MHz, due to the 10-20ns fluorescence lifetime of the nanocrystals. I always like a neat analogy to electronics, and this really demos a case where the systematically tunable optical properties of nanocrystals can be used to achieve something that would be nearly impossible to do using small molecules.