VISUALIZATION OF LASER CAUSTICS IN LIQUID MEDIA UPON STRONG REFRACTION
The paper describes two approaches to using caustics of structured laser radiation passing through optically inhomogeneous medium with essential gradient of refractive index for visualization and determination of properties of this medium. In the first case when wide collimated laser beam illuminates a liquid droplet on a transparent substrate from the bottom up, the caustics on obtained refractive image allows to determine structure of the surface microrelief of this droplet and also contact wetting angle all around its perimeter. In the second case when a diffusive layer of two liquids is rayed through by a laser sheet along the interface, the caustics allows to determine dynamics of changing of thickness of the diffusive layer. The schemes of developed experimental setups are shown, the experimental procedures, results and discussion are given.