ABSTRACT
This chapter reviews a small number of standard texts on acoustic and ultrasonic wave propagation, together with texts on the industrial applications of ultrasonics. It introduces the basic principles of laser operation and the main properties of laser radiation. Energy can be propagated through solids, liquids and gases as acoustic waves. Acoustic waves propagate with a velocity which is characteristic of the fluid medium. The study of laser ultrasonics is somewhat unusual in that it often requires both a pulsed laser to generate the ultrasound, and a continuously running laser to receive the ultrasound. Lasers are characterized by a number of key optical properties, most of which play an important role in the interaction with ultrasonic fields. Their four major optical properties are monochromaticity, coherence, directionality and high intensity. The chapter discusses most common laser systems such as gas lasers, solid state lasers and semiconductor lasers.
