  Experimentally, it turns out that radiation forces from a cw-laser on a
liquid-liquid interface are able to produce giant deformations (up to about
100\mu m), if the system is close to the critical point where the surface
tension becomes small. We present a new model for such a fingerlike
deformation, implying that the system is described as an optical fiber. One
reason for introducing such a model is that the refractive index difference in
modern experiments, such as those of the Bordeaux group, is small, of the same
order as in practical fibers in optics. It is natural therefore, to adopt the
hybrid HE_{11} mode, known from fiber theory, as the fundamental mode for the
liquid system. We show how the balance between hydrodynamical and radiation
forces leads to a stable equilibrium point for the liquid column. Also, we
calculate the narrowing of the column radius as the depth increases. Comparison
with experimental results of the Bordeaux group yields quite satisfactory
agreement as regards the column width.
