ABSOLUTE METER OF PHOTODETECTOR QUANTUM EFFICIENCY BASED ON THE PARAMETRIC DOWN-CONVERSION EFFECT

The quantum phenomena of parametric down conversion have been used for absolute measurement of the photodetector quantum efficiency of ultra -low-light radiation ranging from 10(-12) to 10(-15) W, which is equiv alent to photon fluxes of 10(7) to 10(4) s(-1). The process of paramet ric down conversion gives rise to highly correlated (in time and space ) photon flux pairs. We describe the method, experimental investigatio n, and a new device involving the measurement of the coincidence rate of photodetection of these two correlated beams of light. The coincide nce is lowered by a nonunit quantum efficiency of either detection. Th is fact was used for the definition of the absolute value of both phot odetector's quantum efficiencies.