Experimental investigation of spontaneous parametric noise in lithium iodate and niobate crystals under frequency upconversion conditions

An experimental study was made of the spontaneous parametric noise limiting the maximum sensitivity of near-infrared detectors with a preliminary frequency up-conversion. The angular distribution, polarization, and spectral characteristics of this parametric noise were found to be identical with the corresponding characteristics of the converted radiation, and the noise power was a near-quadratic function of the pump power.