| dc.description.abstract | In recent years, the development of single-photon avalanche diodes (SPADs) grows rapidly because of their potential role in wide applications such as automotive electronics, consumer electronics, medical electronics, quantum key distribution, etc. In all above applications, a highly sensitive and low noise photon detector is always demanded. Special effort is paid to achieve the ability of photon number resolving for facilitating the development of quantum information science. Taking quantum key distribution for example, it requires a single photon detector of the advantages of high speed and high time precision to increase the secure key rate and the transmission distance. A single photon detector capable of resolving photon number can help to prevent the photon number splitting (PNS) attack, ensuring a security communication.
If operating SPAD at conventional gated mode, the alternating current will be coupled to the output through the junction capacitance, resulting an avalanche signal accompanying with the transient signal. Under the operation of high frequency and short pulse width, the reducing amount of avalanche carriers will decrease the avalanche signal, which makes the discrimination of avalanche signal more difficult and is unable to perform reliable counting. Therefore, this thesis employs the self-differencing circuit to eliminate the capacitive signal for suppressing the background noise and better discriminating the avalanche signal such that the dark count rate (DCR), single photon detection efficiency (SPDE), afterpulsing effect and timing characteristics can be improved.
For our home-made SPAD operated at gated mode with the gating frequency of 9.9 MHz, we obtain a suppression ratio of 25 dB by introducing the self-differencing technique. With the improvement in the signal to noise ratio, we have shown that the DCR can be improved by 2 orders. At 225 K, the SPDE is elevated to 74.3 %, approaching the external quantum efficiency. Under the effective gate width of 1.5 ns, we successfully demonstrate the resolution of four photon number states with our home-made SPAD, which is the first demonstration of PNR detector for InGaAs/InAlAs SPADs. | en_US |