Gigahertz bandwidth photon counting

Early applications driving the development of single photon sensitive detectors, such as fluorescence and photoluminescence spectroscopy, simply required low noise performance with kiloHertz and lower count rate requirements and minimal or no timing resolution. Newer applications, such as high data rate photon starved free space optical communications require photon counting at flux rates into megaphoton or gigaphoton per second regimes coupled with sub-nanosecond timing accuracy. With deep space optical communications as our application driver, we have developed and implemented systems to both characterize gigaHertz bandwidth single photon detectors as well as process photon count signals at rates beyond 100 megaphotons per second to implement communications links at data rates exceeding 100 megabits per second with efficiencies greater than two bits per detected photon. With these systems, we have implemented high bandwidth real-time systems using intensified photodiodes, visible light photon counter detectors, superconducting nanowire detectors, Geiger-mode semiconductor avalanche photodiodes, and negative avalanche feedback photon counters.