Abstract

We have investigated the giant thermo-optical mirror effect on the free surface of magnetic fluids under low power continuous wave laser excitation. The essence of this effect is local bending of the free surface of light-absorbing fluid as result of local heating by the laser beam. The phenomenon have been explained through the thermocapillary (Marangoni) effect. The diffraction pattern of the reflected beam (fig.1) has been analyzed in fare field diffraction theory approximation. Calculations of surface bendinn and fluid convection have been performed using lubrication theory approach developed by Cēbers [1]. Interferometric technique has been used for direct observation of shape of the free surface. The existence of the laser-driven thermocapillary convection has been experimentally affirmed by direct observation of the motion of probe microparticles. Thermo-optical mirror experiment has been performed also using a beam with a thin stripe-shape cross-section. The dependence of the surface bending strength on the thickness of fluid layer have been shown.

© 1998 IEEE