Intensity distribution of Gaussian beam transmitting through medium with nonlinear refraction and absorption

The far-field intensity distribution of Gaussian beam transmitting through medium with both nonlinear refraction and absorption was derived and simulated on the basis of diffraction theory. The simulation results show that both the refractive index change of the medium and the wave-front curvature caused by input Gaussian beam influence the radial modulation phase of the beam emitting from the medium exit surface, and that both the medium with selffocusing effect putting in front of the focal point and the medium with self-defocusing effect putting behind the focal point have the diffraction ability similar to blazed gratings which can form a diffraction pattern having a series of bright rings with dark spots in the center of them. If the nonlinear refraction of the media is great, nonlinear absorption affects both the distribution and the intensity of the rings; but if the nonlinear absorption is great, it only affects the intensity.