Absolute internal delay of single photon counting detector

The single photon optical detector is under development for an optical link prepared in the frame of the European Space Agency mission Atomic Clock Ensemble in Space. The objective of this laser time transfer is the optical synchronization of the ground based clocks and the clock on board the International Space Station with precision of the order of units of picoseconds and the accuracy of 50 ps using picosecond laser pulse. The detector package is extremely rugged and compact. The long term detection delay stability in the sense of time deviation is typically 200 fs for averaging times of hours. The change of the detection delay with temperature is typically below 500 fs per Kelvin. The device is capable to operate in a wide temperature range. One particular problem of optical metrology is to determine absolute delay between optical pulse crossing defined reference point of apparatus and the time tagging of this event in a local time scale defined by a signal input to the local time device. The experimental results will be presented showing the internal delay of the photodetector may be determined with the overall accuracy of 13 ps.