Investigation of the acoustic field of a supersonic optoacoustic antenna

A theoretical analysis is made of a laser beam with monochromatically modulated intensity gliding along the surface of an opaque liquid. The region in which the laser radiation is absorbed can be regarded as an extended moving source of sound. An analytic expression for the pressure in the far wave zone is derived and analyzed (the far zone is defined in a coordinate system of a source moving at a supersonic velocity). The directions of propagation of strongest acoustic perturbations are determined (in a coordinate system at rest) for various relationships between the characteristic dimensions of a source, the Mach number, and the wave vector.