Thermal wave propagation in media with thermal memory induced by pulsed laser irradiation

If a sample is exposed to the influence of laser radiation the part of its energy is absorbed and converted into heat. The heat, generated in this way, is transferred through the sample as heat waves, resulting in various effects (for example, photothermal effects). A large number of nondestructive diagnostic methods are based on recording of these effects. In a certain number of materials excited by laser pulses, such as complex biological materials, polymers, metal excited by very short laser pulses, etc., the property of thermal memory become significant. Starting with the hyperbolic equation that describes heat transfer processes of such media, we have developed a model of laser pulse-excited heat waves propagation in order to enable application of photothermal techniques in characterization of these media. The cases of optically opaque and transparent samples are considered. The influence of various backings on photothermal waves has also been analyzed. The results are compared to the previous models. (C) 2003 Elsevier Science Ltd. All rights reserved.10th Tihany Symposium on Radiation Chemistry, Aug 31-Sep 05, 2002, Sopron, Hungar