Nonlinear Laser-induced Deformations of Fluid-fluid Interfaces

An expression for the radiation force from a cw-laser on a fluidfluid interface is derived that is able to model the giant deformations observed in modern experiments when the fluid system is close to the critical point implying that the surface tension is very small. The core of our argument is that the system is modelled as a step-index optical fiber. Then, observing that the dominant HE11 mode in the fiber means a considerable enhancement of the radiation energy density in the central part of the core, we are able to derive in a natural way a reasonably accurate description of the observed effects. To our knowledge this is the first time that a quantitative theory of the giant deformations, experimentally observed in particular by the Bordeaux group, is given. PACS numbers: 42.50.Wk, 47.61.-k, 42.25.Fx