Surface acoustic wave quasi-Bessel beams generated by symmetrically tilted interdigital transducers

Abstract

Formation of surface acoustic wave (SAW) quasi-Bessel beams on a piezoelectric substrate through superposition of plane waves generated by interdigital transducers tilted symmetrically about the propagation axis is numerically and experimentally demonstrated. Acting as an axicon, the tilted transducers provide a facile way for quasi-Bessel beam generation. Finite-element method simulations reveal that non-diffracting Bessel beams, whose length and width are 193 and 1.38 wavelengths, respectively, can be obtained on a YX-128(circle) lithium niobate substrate for an axicon angle of 15 degrees. The corresponding values for 20 degrees are 146 and 1.05 wavelengths, respectively. For a wavelength of approximately 300 micrometers, transmission spectra show that Bessel beam formation can be achieved at frequencies around 13.3 MHz. Bessel beam is visualized through a thin liquid film of methanol on the substrate. SAW Bessel beams can be utilized in acoustophoresis in microfluidic systems and sensing applications.