Gaussian beam representation of beam-like ultrasonic fields

A systematic method of analysis of beam-like wave fields—the Gaussian beam representation—is established in this dissertation. Through a computer determination of the coefficient and beam parameter sets based on optimization theory, any wave field satisfying the condition (ka)² >> 1 can be expressed as a superposition of a number of Gaussian beams with different beam waists, about the same (axisymmetric case) or different beam axes, and propagating in the same direction. Two typical beam fields—the diffraction fields of axisymmetric piston radiators and the non-axisymmetric reflected field of a bounded beam incident at or near the Rayleigh angle— are used as a demonstration of the new method. Experimental results obtained with a new Gaussian transducer are presented as a verifica tion of the physical existence of a single ultrasonic Gaussian beam— the basic unit of the Gaussian beam representation.