Nonlinear interaction of surface acoustic waves in waveguide

A theoretical and experimental study has been conducted on the nonlinear interaction of a surface acoustic wave (SAW) on a surface acoustic waveguide. It is shown theoretically and experimentally that from the parametric mixing phenomenon of two SAW's traveling in the opposite directions, a SAW with the sum frequency is generated which propagates with a certain angle from the waveguide. By changing the frequency difference, the propagation direction of the sum frequency SAW can be controlled freely. The excitation efficiency is such that: it is higher for a narrow waveguide and for a larger velocity variation; and it is periodic with respect to the waveguide width and the period is one wavelength of the sum frequency SAW. Such a generation of the sum frequency SAW and the SAW beam scanning in a plane are possible only with the SAW guided mode. Since the control of the SAW propagation direction in a plane is possible, two-dimensional signal processing is conceivable.