Ultrasonics has made a major impact in many areas, including medical diagnosis and industrial nondestructive testing. As a results of some pioneering work in the 1960s and early 1970s, followed by more systematic studies in the late 1970s and 1980s, laser techniques have now been established as a viable non-contact alternative to piezo-electric transducers for generating and receiving ultrasound. Substantial research has quantified the interactions between the optical and ultrasonic fields, and various potential applications have been demonstrated, mostly under laboratory conditions.