Abstract
In our experiment, we used single carboxyl CdSe/ZnS quantum dots as a single photon source to generate single photon wave packet with a temporal width of 100ns in room temperature. Base on this characteristic, we used acoustic-optic modulator(AOM) to modulate the amplitude and shape of the single photon wave packet in the time domain. We obtained square shape and triangle shape wave packets. In the other part of the experiment, we suppressed the intensity of QD fluorescence in the first tens of nanoseconds, and then measured the second-order intensity correlation g^((2)) (τ) of the modulated wave packet. We successfully purified the modulated single photons. The value of g^((2)) (0) dropped to 0.02, being 33% of its original value, and became a constant value. Moreover, we analyzed the distribution of QD fluorescence in the time domain to build a simple model to obtain the change of amount of biexciton in QD fluorescence. The analysis and our experimental observation are in good agreement, proving the principle of purifying single photons.