Quantum fluctuations at the output of an optical parametric image intensifier

The limiting possibilities of the intensification of weak optical images by means of a parametric traveling-wave intensifier are considered. The signa l-to-quantum noise ratio is compared at the input and output of the intensi fier. Physical conditions are found under which the intensifier is noiseles s; i.e., it does not change the signal-to-noise ratio. Because the parametr ic intensification is sensitive to a phase of the wave front carrying the i mage, the optimum matching of this phase with the intensifier is needed ove r the entire front of the input image. The methods of optimum phase matchin g are described. The spatial resolution of the intensifier is studied as a function of its optical parameters. An apparent paradox of the improvement of the signal-to-noise ratio when the detector area is smaller than the coh erence area of the output radiation is discussed.