Design of Low-Loss Acoustic Delay Lines Enabled by Dual-Mode Interface Acoustic Waves in SiO2/ZnO/IDT/SU-8/SiO2 Structures.

The present work explores the modelling and design of Interface Acoustic Wave (IAW)-based delay lines in SiO2/ZnO (4 µm)/SU-8/SiO2 multilayer stacks and demonstrates that, by properly tailoring the acoustic wavelength and the SU-8 layer thickness, IAW delay lines can achieve performances comparable to, and in some cases superior to, those of conventional Surface Acoustic Wave (SAW) delay lines based on SiO2/ZnO (4 µm) structures. In particular, the proposed devices exhibited untuned insertion losses down to 12 dB, propagation losses as low as 0.052 dB/λ, and electromechanical coupling coefficients K2 approaching 4%, exceeding those calculated for the corresponding SAW devices. The obtained results support the feasibility of compact, high-performance, and potentially packageless acoustic-wave devices for future telecommunications and sensing applications, especially in harsh or contamination-prone environments.