Resonant reflection of a surface acoustic wave from strip waveguides

• The surface acoustic wave (SAW) reflection from a strip waveguide is studied.
• The waveguide supports modes propagating faster than the SAW on the free substrate.
• The substrate is a half-infinite piezoelectric (aluminum nitride).
• The reflection and transmission coefficients exhibit singular resonant behavior.
• The finite element method is used.

A numerical study is performed of the oblique reflection of a surface acoustic wave from a strip of finite width deposited on the surface of a half-infinite substrate. The finite element method is used. If the strip–substrate contact supports waveguide modes with the velocity exceeding the surface wave velocity on the free surface of the substrate, then an interval of angles of incidence exists where the surface wave efficiently excites a waveguide mode. The excitation of the waveguide mode is accompanied by a singular behavior of the reflection and the transmission coefficients. The dependence of the magnitude and the phase of the coefficients on the angle of incidence, the frequency, the width and the thickness of the strip is examined. In particular, it is found that the magnitude of the reflection coefficient abruptly almost vanishes and abruptly increases almost to unity within the resonance interval of angles of incidence.