  It is well accepted that an outward Marangoni convection from a low surface
tension region will make the surface depressed. Here, we report that this
established perception is only valid for thin liquid films. Using surface laser
heating, we show that in deep liquids a laser beam actually pulls up the fluid
above the free surface generating fountains with different shapes. Whereas with
decreasing liquid depth a transition from fountain to indentation with fountain
in-indentation is observed. Further, high-speed imaging reveals a transient
surface process before steady elevation is formed, and this dynamic deformation
is subsequently utilized to resonantly excite giant surface waves by a
modulated laser beam. Computational fluid dynamics models reveal the underlying
flow patterns and quantify the depth-dependent and time-resolved surface
deformations. Our discoveries and techniques have upended the century-old
perception and opened up a new regime of interdisciplinary research and
applications of Marangoni-induced interface phenomena and optocapillary fluidic
surfaces-the control of fluids with light.
