Surface-acoustic-wave device

Abstract

A surface-acoustic-wave device comprises a piezoelectric substrate and first and second comb-shaped electrodes each having a bus-bar portion parallel to a propagation direction of a surface acoustic wave in the substrate. Respective electrode fingers are periodically formed on the piezoelectric substrate and extend in directions perpendicular to the propagation direction, wherein the electrode fingers of the first comb-shaped electrode and the electrode fingers of the second comb-shaped electrode are separated away from the bus-bar portion of the opposing comb-shaped electrode. The respective electrode fingers being periodically arrayed in the propagation direction of the surface-acoustic-wave, and the electrode fingers of each comb-shaped electrode are inclined at root portions thereof outwardly right and left from the bus-bar portion of the corresponding comb-shaped electrode so that the inclined portions of the electrode fingers face a direction of a leaking surface-acoustic-wave perpendicularly.

1 . A method of designing a surface-acoustic-wave device, comprising the steps of:
 providing an elastic-wave monitoring device to monitor a distribution of a surface-acoustic-wave in the surface-acoustic-wave device; and   determining a configuration of the surface-acoustic-wave device based on the distribution of the surface-acoustic-wave monitored by the elastic-wave monitoring device,   the elastic-wave monitoring device comprising:
 an optical system arranged so that a circularly polarized light from a light source is incident to the surface-acoustic-wave device and a light beam from the surface-acoustic-wave device passes through a polarizing filter to a photodetector; and 
 a detection unit detecting periodic fluctuation components of an output signal of the photodetector, 
 wherein the polarizing filter is arranged to have a polarization transmission axis directed to one of directions of principal axes of an ellipse formed by intersections of an index ellipsoid of the surface-acoustic-wave device and a plane perpendicular to an incidence direction of the light beam and passing through an origin of the index ellipsoid. 
   
   
   
       2 . The method of  claim 1 , wherein the surface-acoustic-wave device comprises an inter-digital transducer formed on a piezoelectric substrate, and the elastic-wave monitoring device monitors a position and direction of a leaking elastic wave leaking out of the inter-digital transducer, and, in the determining step, the configuration of the surface-acoustic-wave device is determined such that the leaking elastic wave is reflected towards the inter-digital transducer.