Laser interferometric measurement of the vibration displacements of a plano-convex AT-cut quartz crystal resonator

Detailed vibrational displacement distributions of the thickness-shear modes of a plano-convex AT-cut quartz plate have been measured for the first time utilizing a laser interferometric technique. The technique is unique in that simple introduction of a low-frequency phase modulation into one of the laser beams makes measurements essentially free from the environmental mechanical disturbances, and hence relatively simple optical setups may be used for measuring in-plane vibration displacements down to the order of several angstroms.