Abstract
Acoustic waveguides of LiNb0,and quartz have been examined. The guides studied have wedge-shaped cross sections with one surface coplanar with the top surface of the substrate wafer. The waveguides are formed by using orientation dependent etchants to selectively etch the top surface of the wafer, leaving wedge-shaped overhanging structures for wave guiding. Waveguides with top angles of about 60 and lateral surface dimensions on the order of 25 microns have been etched on quartz. The lateral surface smoothness and apex roughness of the guides are less than 0.1 micron. Similar guides have been etched in LiNb03 but the lateral surface smoothness results are currently limited by etch-mask erosion. been fabricated and tested. Results at 1 MHz on PZT show that extremely high impedances are encoun- tered. If impedance matching is carried out and the transducers are f abricated with concern for spurious pad modes, then insertion losses under 10 dB (including the matching networks) are easily obtainable. In addition, t he responses are free from spurious modes with rejection in excess of 50 dB at the zero'es of the transducer spectrum. Low frequency prototype waveguides with wedge-shaped geometries have
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