The thermoconvective flow induced in oil samples and oil-in-water emulsions by irradiation with a laser beam is studied experimentally. The samples are irradiated by He-Ne and CO<sub>2</sub> lasers at different power levels. Time-resolved records of temperature and surface waves that propagate in a liquid surface are presented. In laser-heated emulsions the thermoconvective flow leads the dispersed oil droplets to the water-free surface where they agglomerate to form a floating oil layer. The reflected light beam is formed by a speckle pattern whose intensity and contrast show a spiking, quasi-periodic time variation. A theoretical model is proposed to explain this phenomenon.
© 2002 Optical Society of America
(120.0280) Instrumentation, measurement, and metrology : Remote sensing and sensors
(240.6690) Optics at surfaces : Surface waves
(290.5850) Scattering : Scattering, particles
(310.3840) Thin films : Materials and process characterization
(350.5340) Other areas of optics : Photothermal effects
Germán Da Costa, Juan Enrique Parra, and Felix Mosqueda, "Laser-Induced Migration of Oil Particles Suspended in a Water Matrix," Appl. Opt. 41, 6420-6430 (2002)