Investigation into the photon counting performance of InGaAs/InP separate absorption, grading and multiplication avalanche photodiodes at a wavelength of 1.55μm

The ability to detect single photons at a wavelength of 1.55μm is of particular importance for applications such as quantum cryptography, optical time domain reflectometry and time-resolved photoluminescence, as well as several other applications. This has led to investigations of alternative long wavelength SPAD detectors, fabricated from InGaAs/InP, which show greater potential for operation at wavelengths of 1.55μm or above. This research concentrates on the characterisation of commercially available InGaAs/InP avalanche photodiodes, not specifically designed for single photon detection. A comprehensive study has been performed into the dark noise, detection efficiency and timing response of many commercially available InGaAs/InP detectors at temperatures between 77K and room temperature at a wavelength of 1.55μm. Results show that the photon counting performance of such devices, at 1.55μm is comparable to, or in some cases better than, the performance of germanium detectors at 1.3μm. An optical time domain reflectometer (OTDR) and a partial quantum cryptography demonstrator were constructed incorporating one of the InGaAs/InP avalanche photodiodes. The time resolution of the OTDR system was found to be superior to commercially available non-photon-counting alternatives. The potential range of the partial quantum cryptography system was shown to be in excess of 100 km, twice the distance currently achievable with germanium-based 1.3μm wavelength systems. (author)