EXPERIMENTAL-DETERMINATION OF THE EFFECT OF POLARIZATION OF THE HEATING LASER-PULSE ON THE CHARACTERISTIC DECAY TIME CONSTANT AND FOCAL LENGTH OF THERMAL LENSES, AND ON THE THERMAL DIFFUSIVITIES IN PURE LIQUIDS

The characteristic decay time constant of defocusing thermal lenses was determined in pure benzene, water, chloroform and nitrobenzene, with the use of non-polarized and linearly polarized single heating pulses of a Nd:YAG laser. From the characteristic time constants, the thermal diffusivities were calculated and compared with those obtained through the known values of thermal constants of the homogeneous liquids. From the course of decay of the thermal lenses, their focal lengths at the beginning of the decay process were determined. Generally, the characteristic decay time constants were found to be smaller, the focal lengths longer, and the thermal diffusivities greater with polarized than with non-polarized heating pulses. The difference is interpreted in terms of the unidirectional alignment of induced dipoles by the linearly polarized heating pulse.