Tunable Source of Bi-Photon Radiation Based on Spontaneous Parametric Scattering

source of correlated photon pairs based on spontaneous parametric scattering is developed and created. The source may be used both as a probabilistic source of single-photon radiation with low value of the parameter g (2) (0) and as a bi-photon source for the quantum distribution of keys based on the Einstein–Podolskiy–Rosen paradox as well as for the Klyushko–Penin reference method of determining the quantum efficiency of detectors of low-photon radiation. Experimental results of the generation of bi-photons for pairs of wavelengths of 651 nm (signal wave) and 1100 nm (idler wave) are presented. The quantum efficiency of a low-photon 651-nm wavelength detector is measured by means of this source using the Klyushko–Penin reference method. The new source may be tuned comparatively easily over a broad range of wavelengths from 558 to 1550 nm.