Point spread function of a four-wave radiation converter in a multimode waveguide with Kerr nonlinearity

An expression is obtained for the point spread function of a four-wave radiation converter in a multimode waveguide with Kerr nonlinearity, taking into account the transfer of energy from the object wave to the signal wave and vice versa. For single-mode pump waves, the presence of «generation» points is shown and conditions are found on the waveguide parameters, characteristics of the interacting waves, under which the «generation» condition is realized. In the vicinity of the «generation» points, the shape of the point spread function is determined by one of the waveguide modes, the number of which coincides with the number of the pump wave mode. For a four-wave radiation converter in a waveguide with infinitely conducting surfaces, the quality of the wavefront conjugation near the second «generation» point coincides with the quality of the wavefront conjugation at a low reflection coefficient. For a four-wave radiation converter in a parabolic waveguide near the second and next «generation» points, the shape of the point spread function is determined by one of the waveguide modes.