Parametric image amplifiers with correction of the gain inhomogeneity

A longitudinal shift of the amplified and converted images of a beam focussed in a nonlinear component are determined. This shift is related to a change in the effective wave number in the course of parametric amplification. When the gain is considerable, the dependence of this shift on the pump intensity is weak and it does not reduce the resolving power. It is also shown that an inhomogeneity of the distribution of the gain over the field of view can be corrected in the second stage of an amplifier which amplifies the angular spectrum of the radiation transmitted by the first stage.