Phase sensitive laser probe for high-frequency surface acoustic wave measurements

Field measurements of surface acoustic waves can be performed by coherent light in several ways. A method is described where a laser beam is focused to a small spot on the surface to obtain phase and amplitude infomation. A modified knife-edge technique has been applied in combination with amplitude modulation of the laser beam and single-side-band modulation of the surface wave. The apparatus has proven to be a powerful and flexible analytical tool. It is able to retieve phase and amplitude information from a traveling wave, and a partially standing wave can be characterized in terms of phase and amplitude of its two haveling wave components. The apparatus has been used up to 450 MHz.