Self-focusing of laser beam in dispersed medium

Water suspension of absorbing nano-sized particles is an example of a medium in which non-linear effects are present at moderate light intensities, which is applicable to optical treatment of biological objects. The experiment was dedicated to the phenomena emerging in a thin layer of such a medium under the action of inhomogeneous light field formed due to the Pearcey diffraction pattern near a microlens focus. In this high-gradient field, the light energy absorbed by the particles induces inhomogeneous distribution of the medium refraction index, which results in observable self-diffraction of the falling light, depending strongly on the medium position with respect to the focus.