Abstract
We report on the generation of polarization-correlated photon pairs by the radiative biexciton (XX)-exciton (X) cascade of single CdSe quantum dots (QDs). Under nonresonant optical pulsed excitation (76 MHz) at low temperature (4 K), a high collinear correlation degree of 74.5% was observed from cross-correlation measurements between single XX and X emissions, which reflects an asymmetry-induced exciton fine-structure splitting. In consideration of the excitonic radiative lifetime (250 ps) this effect allows for direct conclusions about the relaxation time (T⩾480 ps) between the corresponding sublevels. Our results also suggest that the biexciton-exciton cascade in a CdSe QD is well suited for triggered single photon and/or photon pair generation rates above 1 GHz.
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