Resonant excitation of a thin waveguide with an elliptical reflector for high-power ultrasound (ELIPS)

Abstract

High-power ultrasound plays a critical role in various applications, yet generating multi-frequency ultrasound in a localized area with a single transducer remains a significant challenge. We propose a transducer with an elliptical reflector to excite a thin waveguide at multiple frequencies within the megahertz range. The elliptical reflector transforms a plane dilatational wave from the piezoelectric elements into a transverse wave, focused on the thin waveguide using mode conversion. The use of transverse waves reduces energy loss during the reflection process and achieves a smaller focal diameter. Finite element analysis verified wave focusing with the elliptical reflector and the thin waveguide excitation. The fabricated prototype achieved high vibration velocities at the central tip of the waveguide, including 6.7 m/s at 1.767 MHz and 12.8 m/s at 0.411 MHz. At 1.767 MHz, the vibration velocity increased linearly with increasing applied voltage, suggesting the potential for achieving even higher velocities with greater energy input. At 0.411 MHz, the stress within the thin waveguide was expected to exceed the material's tensile strength, indicating that the design maximized the material's performance limits.