dc.description.abstract | Single photon avalanche diode (SPAD) having the most sensitive capabilities becomes an essential technology for the development of photonic quantum science. Among them, fiber-based quantum key distribution (QKD) and quantum computer are the technologies that urgently need to be developed for their potential applications of national defense security and encrypted bank security. Therefore, InGaAs/InP single-photon avalanche diode capable of detecting the optical communication wavelength range becomes the best choice for a portable and lightweight single photon detector. It has already been commercialized and exhibits high quantum efficiency and low dark count, and thus is expected to improve the performance of quantum key distribution and quantum computers. In addition to single-photon click on/off detection, single photon detector with photon number resolving capability plays an indispensable role in the above quantum technologies. It prevents the quantum key distribution from the attack of photon number splitting and is also instrumental to the development of continuous-variable quantum computing.
Due to numerous defects in single photon avalanche diode of III‑V semiconductor, the gated mode is often used to regulate the generation of carriers to suppress the afterpulsing caused by the defects. However, the pulsed waveform is coupled to the output signal through the diode junction capacitance, which will be superimposed onto the avalanche signal, making the avalanche signal difficult to be identified. So, it is necessary to further increase the bias voltage to improve the signal-to-noise ratio (SNR), however, high bias operation will generate infinite avalanche carriers which hinders the realization of photon number resolving. To achieve photon number resolving, it is necessary to shorten the gate-on time to regulate the number of avalanche carriers, that is to quench the device before reaching infinite gain. However, the avalanche signal becomes smaller for shorter gate-on time. Thus, the elimination of the capacitive signal becomes an important issue. To discriminate avalanche signal from the capacitive signal in the pulsed gated mode, a self-differencing circuit is often used to subtract the common-mode capacitive signals; Or, sine wave gated mode with filtering technology can also be used to eliminate the capacitive signal to improve the signal-to-noise ratio for better discriminating the avalanche signals.
In this work, a sine wave gated mode is used for SPAD operation. Different from the setting of the traditional pulse gated mode, the gate-on time of the sine wave gated mode is determined by the center frequency of the sine wave. Which is to say, the gate-on time can be reduced simply by increasing the center frequency. We adopt a center frequency of 300 MHz for the full characterization of a commercial SPAD and to examine the capability of photon number resolving. In this work, a filter technique is used to reduce the discrimination level of avalanche signals to 10 mV and the common mode rejection ratio is 55.9 dB, succeeding to identify tiny avalanche signals. Based on sine wave gated scheme, we have fully characterized the commercial SPAD at various temperatures and demonstrated photon number resolving capability of InGaAs/InP SPAD. | en_US |