Fluctuation-dissipation theory of four-photon parametric frequency upconverters

Fluctuation-dissipation theory is developed for parametric noise in a four-photon frequency upcon verter of infrared signals. General analytic formulas are obtained for the parametric converter efficiency, as well as for the signal/noise ratio and the threshold sensitivity. The most important dependences of these characteristics on the parameters of the problem are analyzed and the optimal conditions for the realization of a parametric converter are determined.