Generation of sound in a liquid as a result of absorption of modulated laser radiation

A theoretical analysis is made of the excitation of sound in a liquid as a result of absorption of timemodulated optical radiation. Attention is concentrated on steady-state generation of monochromatic sound resulting from quasicontinuous irradiation of the liquid. The patterns established in the far and near acoustic wave zones are considered; definite advantages of the far-zone generation are pointed out. The optimal modulation frequency ensuring the maximum amplitude of the acoustic wave in the far zone (for given laser radiation power) is considered. A statistical analysis is made of the influence of random inhomogeneities in the transverse distribution of the intensity of a laser beam. Numerical estimates are obtained for the generation of sound in water by СO₂ and YAG laser radiations.