One of actual and promising method of researching optically inhomogeneous media by using electromagnetic radiation is the method of the laser refractography. It is based on the phenomenon of refraction of structured laser radiation in optically inhomogeneous media and registration of its form deviations with the digital video camera. The case when inhomogeneity in liquid is created by diffusion. It was researched conditions for the occurrence of caustics in longitudinal probing of optical stratified inhomogeneous media by plane and cylindrical laser beams were researched in this work. Experimental setup for caustics visualization was shown. The method was shown for solving the inverse task of finding properties of the medium by analyzing caustics’ location.