Fast and reversible excited state absorption in II-VI-based nanocomposite thin films

Abstract

Nanocomposite CdS-ZnO thin films deposited directly on quartz substrates by high-pressure magnetron sputtering show a completely reversible photodarkening at a very low threshold intensity (similar to 1 kWcm(-2)), and a moderately fast recovery time (< 1 ms). This makes them ideal in optical limiting applications for both continuous wave as well as high rep-rate pulsed lasers. The same system also shows an intensity-dependent quenching of the photoluminescence. Using a pump-probe experiment, we show that photodarkening in such a quantum-dot thin film originates from excited state absorption. (c) 2005