Investigation on the formation of second-order-hot-image-like fringes

Based on the optical path model for nonlinear imaging, we systematically investigated the propagation of flat-topped Gaussian beam which is modulated by two parallel phase-typed wirelike scatterers through computer simulation. It is found that, under certain conditions, there is no intense second-order hot image fringe in the predicated plane half-distance from the medium to the scatterer, but there are other two intense fringes whose in-beam positions are some distance deviated from those of the scatterers. These intense fringes are called second-order-hot-image-like fringes in this paper. When compared with the corresponding single scatterer case, the intensity level of the fringes is close to that of second-order hot image fringe. Besides, there are also hot images, but their intensities are much lower. The influence of the phase modulation depth of the scatterers on the propagation for both double and single scatterer cases is also investigated. First, as the phase modulation depth increases, the fringe intensity changes same as second-order hot image fringe does and their intensities keep very close to each other. Second, the fringe intensity increases at first and then decreases in a certain value range of phase modulation depth, but the hot image intensity changes inversely. Third, in the Kerr medium, the maximum intensity of the beam in the double scatterer case is higher than that in the single scatterer case except for the phase modulation value section around three rad.