Long-range ladar, spectroscopy, and quantum-key-distribution systems require subnanosecond real-time single-photon-counting detectors. Researchers at Epitaxial Technologies (Baltimore, MD), NASA Goddard (Greenbelt, MD), and the Air Force Research Lab (Wright-Patterson AFB, OH) have reported development of such a high-performance detector operable in the 1064 to 1550 nm spectral range. These high-gain, high-sensitivity avalanche photodiodes (APDs) are capable of single-photon counting in the linear mode below the breakdown voltage and at room temperature.
The aluminum indium arsenide/gallium indium arsenide APDs have multiplication gains as high as 347,000, sensitivities of -69 to -77 dBm, and photon-detection efficiencies as high as 27%. The single-photon-counting APDs are free of after-pulse artifacts even for pulse widths in the nanosecond range. They can detect single photons at up to 138 MHz and have the capability for gigahertz repetition rate. Based on APD production technologies, the APDs have excess noise factors as low as 2 with the high gain. The researchers claim these are the highest multiplication gains simultaneous with low excess-noise factors and high sensitivities reported so far for long-wavelength APDs. Contact Leye Aina at [email protected].
