Experiments with Love waves on layered glass

Love waves are horizontally polarized shear waves (SH waves) guided along a surface by a low-velocity layer which covers a higher velocity substrate. In our experiments this low-velocity layer is a thin sheet of glass bonded to a very thin (32 micron) polymer film. The film in turn is bonded to a much thicker soda-lime glass base plate. We are using two transducers which can be moved freely about the glass surface, to vary the distance between them or to check the glass for uniformity. In these transducers, longitudinal waves at 5.6 MHz are first converted to bulk shear waves by reflection from a tilted surface; the shear waves are then focused upon a wedge-shaped edge which rests on the glass under gentle pressure and vibrates so as to generate SH waves in the glass. Group velocity, phase velocity and propagation loss were measured on substrates using several kinds of glass and various polymers. Experimental data correlate well with computation and indicate that some of these compound plates could make excellent touch-sensitive panels.