Lens effect due to the deformation of a liquid surface caused by the thermal action of laser radiation

An analysis is made of the formation of a surface lens due to the thermal expansion of an inhomogeneously heated material in a laser radiation field. The focal lengths are determined. An analysis is made of the surface thermal focusing dynamics and this is compared with other nonlinear effects. It is shown that for thin layers and also when surface absorption occurs, surface thermal focusing may be the dominant lens effect.