Laser‐generated ultrasonic beams

Laser-generated ultrasonic beams.

Tailoring ultrasonic beams with optoacoustic holography

A combination of laser-induced ultrasound generation and ultrasonic holography for spatial control of the generated ultrasonic pulse is presented. Ultrasound is produced by absorption of laser pulses at an absorbing layer in a water tank via the optoacoustic effect. In order to produce a defined ultrasonic frequency in the MHz range, the laser pulses are harmonically time-modulated using an aco...

High-resolution photoacoustic imaging with focused laser and ultrasonic beams.

We report a photoacoustic imager that utilizes a focused laser beam in combination with a 20 MHz ultrasound focusing transducer to obtain micron-resolution tissue images over a long working distance. The imager is based on a ring transducer that combines ultrasonic and laser beams collinearly and confocally in a monolithic element. The combination of focused laser beam and short pulse irradiati...

Focal shift of convergent ultrasonic beams reflected from a liquid- solid interface

In 1947, Goos and H•inchen • reported the first experimental evidence of the lateral displacement of a light beam upon total internal reflection. Only a few years later, Schoch 2 found the acoustical equivalent ofthis phenomenon by schlieren photography. Schoch's results showed that the center of an ultrasonic beam reflected from a liquid-solid interface is displaced by a certain amount along t...

A paraxial theory for the propagation of ultrasonic beams in anisotropic solids

The necessity of nondestructively inspecting cast steels, weldments, composites, and other inherently anisotropic materials has stimulated considerable interest in wave propagation in anisotropic media. Here, the problem of an ultrasonic beam traveling in an anisotropic medium is formulated in terms of an angular spectrum of plane waves. Through the use of small angle approximations, the integr...