Acoustic field of an optoacoustic antenna moving at subsonic or supersonic velocity

A theoretical investigation is made of the acoustic field generated by a monochromatic intensity-modulated laser beam scanning uniformly the surface of an opaque liquid. The laser radiation absorption region is an extended moving sound source which can be described neglecting the flow. Analytic expressions are derived for the pressure in the far wave zone modified by the motion. The angular distributions are analyzed. It is shown in particular that the fundamental characteristics of a broad disk-type antenna do not vary over a wide range of sub- and supersonic antenna velocities. Numerical estimates are made for various typical cases.