dc.description.abstract | Single-photon avalanche diodes(SPADs) with photon-number-resolving (PNR) capability can operate at near-room temperature and maintain a lower level of dark count rate, making them indispensable in the field of quantum research. Taking single-photon lidar(SPL) as an example, these devices utilize their high sensitivity to single photon to enable the detection of distant targets. However, this sensitivity also makes SPADs susceptible to non-ideal factors such as ambient light, which increases the difficulty of data processing. If further equipping SPADs the capability of PNR with an advanced technique, it becomes possible to eliminate the weak avalanche signals caused by ambient light from the data, significantly improving data accuracy. In the above applications, increasing the operating frequency of SPADs means being able to detect a larger amount of data within the same time, effectively enhancing data integrity. However, while increasing the frequency, it also amplifies the avalanche signals caused by non-ideal factors, thereby increasing the difficulty of post-processing the data. Therefore, operating the device at high frequencies while maintaining a low level of dark count rates poses a significant challenge in terms of device structure design and external circuitry.
In the traditional gated-mode, the avalanche signals of the device can be buried by the capacitance signal generated by the internal junction capacitance. This requires increasing the excess bias to successfully count the signals. However, at higher excess bias, the device may saturate due to excessive current, making it unable to resolve the photon number. Currently, there are many studies that have proposed successful methods to extract the avalanche signals from the capacitive signal. Techniques such as self-differencing(SD) circuits and sinusoidal gate-mode with filters have been used. These techniques eliminate the capacitance signal and allow the device to operate at lower excess bias, avoiding saturation caused by excessive avalanche current and enabling successful PNR.
Due to the 9.9 MHz operating frequency of the SD circuit used in the laboratory, a 20 meters delay line was required for delay, resulting in severe signal attenuation. The capacitance signal could not be completely eliminated, necessitating a higher bias voltage for the detection of breakdown signals. This led to an increase in dark counts and posed challenges for PNR measurements. To address these issues, this study redesigned a SD circuit suitable for high frequency, increasing the operating frequency from 9.9 MHz to 104.731 MHz. The length of the delay line was shortened to 3 meters, successfully reducing the capacitance signal to a lower level. As a result, weaker breakdown signals could be detected, mitigating the impact of dark counts on the component and significantly aiding in PNR measurements.
This study employed gated-mode with a redesigned SD circuit, taking advantage of the shorter delay line to successfully reduce the capacitance signal to 3 mV. The noise suppression ratio increased from 25 dB to 37.6 dB compared to the previously used SD circuit. At 200 K, the single-photon detection efficiency(SPDE) reached 52 %, and the performance of PNR was evaluated at different temperatures. To further explore the impact of operating frequency on the component′s performance, the study compared the effects at high and low frequencies, as well as the influence of different component gains on PNR. The analysis addressed challenges faced by the component at both high frequencies and high gains, proposing effective solutions. | en_US |