Theoretical and experimental investigation of nonlinear optoacoustics in liquids

The optoacoustic effect in liquids has been studied theoretically and experimentally. Measurements were taken in various liquids studying the thermal expansion mechanism and comparing these results to existing theoretical predictions. Among the quantities investigated were the dependence of optoacoustic amplitude on optical absorption coefficient, thermal expansion coefficient and laser pulse energy. These experimental observations were found to be in agreement with theory. The signal amplitude was also measured as a function of propagation distance. It was found that the optoacoustic amplitude varies as 1/{dollar}sqrt{lcub}rm r{rcub}{dollar} which is characteristic of a cylindrical source. Measurements were also taken in liquid Carbon Disulfide (CS{dollar}sb2{dollar}). The strong absorption of the 337 nm radiation resulted in a nonlinear relationship between optoacoustic amplitude and input energy. These nonlinear variations were explained in terms of dynamically changing temperature dependent coefficients of thermal expansion and optical absorption.