Six-photon resonance parametric up-conversion in a nonmonochromatic pump field

Six-photon parametric up-conversion under conditions of two-, three-, and four-photon resonance of a constant nonmonochromatic pump field is analyzed allowing for population migration, transient response of the medium, Stark shift of the levels, and width of the frequency spectrum of the the pump field. It is found that in the steady-state conversion regime, the maximum average conversion efficiency in the four-photon resonance case differs only negligibly from the maximum conversion efficiency in a monochromatic field, whereas in the two-photon and three-photon resonance cases it is higher than the maximum efficiency in a monochromatic pump field. An analysis is made of the influence of optically induced relaxation on the average conversion efficiency under conditions of pulsed excitation of two-, three-, and four-photon resonances.