Control of High-Frequency Surface Acoustic Waves via Transducer Geometry and Higher-Order Mode Equivalency

GHz-range surface acoustic waves (SAWs) are essential for high-frequency sensing, hybrid photonic-phononic, and quantum devices. However, SAW generation via interdigital transducers (IDTs) on piezoelectric substrates faces significant scaling and attenuation challenges, besides being incompatible with silicon-based electronics due to the lack of piezoelectricity. Here, we demonstrate fundamental and higher-order SAW generation and detection in monolithic silicon using metallic transducers and time-resolved extreme ultraviolet diffraction measurements. Our results, supported by finite-element simulations, establish the equivalence of first- and second-order SAW frequencies (ν) and attenuation lifetimes (τS) over wide ranges spanning 3.5–16.5 GHz and 14–0.6 ns, respectively, that allow high-frequency SAW generation with large τS in the same device. We further show that τS is tunable via transducer geometry, achieving second-order SAWs (2ν) near 10 GHz with τS ≈ 5 ns. These findings reveal lower acoustic losses in silicon than those reported with IDTs on piezoelectric substrates.