High resolution resonant photoluminescence excitation of $CdSe∕ZnS$ nanocrystals at low temperatures

We present a new technique to perform high resolution resonant photoluminescence excitation of $CdSe∕ZnS$ nanocrystals. The method takes advantage of the long photoluminescence decay times $(∼1μs)$ observed in this system at liquid helium temperatures. Resonant photoluminescence excitation can be performed using a tunable pulsed excitation and a time-gated detection. Spectral hole burning investigations on an ensemble of $CdSe∕ZnS$ nanocrystals lead to homogeneous linewidths of $∼100μeV$ for the band edge exciton state.