Quality of wavefront reversal for four-wave interaction in a multimode waveguide with thermal nonlinearity

For a four-wave radiation converter in a two-dimensional multimode waveguide with thermal nonlinearity at a low reflection coefficient, we analyze the influence of the spatial structure of pump waves on the quality of wavefront reversal. It is shown that the half-width of modulus of the point spread function of a four-wave radiation converter decreases with decreasing radius of Gaussian pump waves on the waveguide edges, leading to an improvement in the quality of wavefront reversal. For a four-wave radiation converter in a two-dimensional waveguide with infinitely conducting surfaces, we show the presence of "generation" points, near which a sharp increase in the object wave amplitude is observed, with its form completely determined by one of the waveguide modes.