Gigahertz Bending Acoustic Waveguides in Aluminum Scandium Nitride Film

This paper presents a bending acoustic waveguide based on focusing single-phase unidirectional transducer (FSPUDT) by utilizing Al<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.7</inf>Sc<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</inf>N thin film. By Al<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.7</inf>Sc<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</inf>N focusing acoustic waves into wavelength-scale structures, the FSPUDT enhances the coupling between narrow waveguides and transducers. Four waveguide structures have been designed to investigate the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{S}_{21}$</tex> characteristics. The 45° bending waveguides outperform the straight and 90° bending waveguides, achieving a reduction in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{S}_{21}$</tex> of 2.75 dB and 10.24 dB at 0.96 GHz, respectively. The Bezier waveguide exhibits an <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{S}_{21}$</tex> of -31.81 dB, which is very close to the 45° bending waveguide. This work highlights the potential of using Bezier and 45° bending waveguide design, demonstrating superior performance and efficiency, suggesting promising advancements in waveguide technology for phononic integrated circuits (PnICs).