Low-power laser driving of a binary liquid

We have investigated the interaction of a laser beam with a near-critical binary liquid by observing how the growth of the concentration gradient due to gravity (the barodiffusion gradient) is modified by the presence of the beam. We observe definite evidence of laser driving in the system: The size of the steady-state barodiffusion gradient increases with increasing laser power, and the system exhibits different dynamical behaviors in the limit of high and low powers. Since our results cannot be explained by a purely diffusive model, we conclude that convection must be important in the system and present an estimate of the laser power at which convection should become significant.