Self-differencing Gated SPADs Achieve Dead-time-free Operation at 100MHz Repetition Rate for High-speed Photon Counting

Single-photon avalanche diodes are crucial components in advanced technologies, including quantum computing and high-speed light detection, but operating these detectors at very high repetition rates presents significant challenges. Samuele Altilia, Edoardo Suerra, and Stefano Capra, alongside colleagues at their institutions, now present a simplified and highly effective method for eliminating dead-time in these detectors, enabling continuous operation at 100MHz. Their innovative self-differencing gating scheme dramatically reduces the complexity of previous designs while simultaneously improving detector efficiency and signal-to-noise ratio. This achievement unlocks the potential for continuous single-photon detection, paving the way for detectors that could ultimately operate at the gigahertz level and significantly advance applications reliant on precise and rapid light measurement.

Dead-time Free SPAD Readout Scheme Demonstrated

Single-photon avalanche diodes (SPADs) are crucial for applications like time-correlated single-photon counting, fluorescence lifetime imaging, and quantum key distribution. Conventional SPAD readout schemes suffer from dead time, limiting maximum count rates and introducing inaccuracies. Researchers have developed a minimalist self-differencing gating scheme that overcomes these limitations, enabling dead-time-free operation of SPADs at high repetition rates, and actively suppresses afterpulsing, a major source of noise. By implementing a self-differencing approach, the circuit subtracts afterpulsing from the main signal, substantially reducing false counts.

The method precisely analyzes the SPAD output, coupled with a fast gating mechanism that selectively counts photons only during the active detection window, ensuring the recorded count rate accurately reflects the incoming photon flux, even at high repetition rates. The key achievement lies in a simplified gating circuit that achieves dead-time-free operation with minimal complexity, utilizing commercially available components. The results demonstrate the proposed scheme effectively eliminates dead time, enabling a maximum count rate limited only by the SPAD characteristics and electronic readout speed. Furthermore, the method significantly improves the signal-to-noise ratio, enhancing the overall performance of the SPAD detector, and paving the way for more accurate and efficient single-photon detection.

Fast Gated SPAD Detector for Quantum Technologies

This research details the design, fabrication, and characterization of a novel SPAD detector optimized for high-speed operation, specifically targeting applications in quantum technologies. Existing SPAD detectors often struggle with high repetition rates due to limitations in quenching and recovery times. Researchers developed a simplified gated quenching scheme for SPADs, aiming to reduce complexity while maintaining high performance, and designed the detector to operate at a 100MHz repetition rate. The detector exhibits good quantum efficiency and a low dark count rate, minimizing false detections due to thermal noise.

It also demonstrates low afterpulsing. Crucially, the detector’s recovery time is faster than the pulse period, enabling continuous operation at 100MHz, a significant achievement. The quenching circuit is simpler than many existing designs, potentially leading to easier integration and lower cost. The developed SPAD detector successfully achieves high-speed operation at 100MHz. The simplified quenching scheme proves effective, and the detector’s characteristics make it a promising candidate for various quantum technologies. This represents a significant advancement in SPAD detector technology, offering a high-performance, simplified solution for applications demanding fast and reliable single-photon detection.
MHz Gated SPAD Detector Achieves Continuous Operation

This research presents a novel scheme for gated quenched SPAD detectors, designed for high-repetition-rate operation at 100MHz. Researchers successfully simplified existing self-differencing techniques while simultaneously improving detector performance and control. Experimental characterization demonstrated good quantum efficiency, a low dark count rate, and minimal afterpulsing, confirming the device’s capabilities. Importantly, the detector exhibits a recovery time faster than the pulse period, enabling continuous operation at 100MHz and suggesting potential scalability to even higher repetition rates. Researchers confirmed that the detector behaves as an ideal instrument in pulsed operation, with full efficiency recovery within a single pulse repetition. This achievement represents a significant step towards enabling high-speed quantum technologies by providing a simple and integrable approach to SPAD operation.