Higher-order topological SAW devices towards topological signal filtering and processing

Topological crystals provide a transformative platform for chip-scale signal processing, offering exceptional robustness, precise wave manipulation, and ultra-compact integration. However, their extension to phononics, particularly for controlling surface acoustic wave (SAW), has thus far been limited to lower-order topological states. This restriction confines their functionality primarily to protected transport while lacking essential features such as frequency-domain processing, tunability, and multifunctionality—key challenges that severely hinder their adaptability and potential to revolutionize signal processing devices. To fill this gap, we experimentally demonstrate a higher-order topological SAW device capable of both time-domain and frequency-domain topological signal processing. By leveraging coupling effects, we achieve multimode coordination and significantly enhance tunability, enabling precise control over wave leakage suppression, blocking, and selective conduction within an ultra-compact footprint. More importantly, our system exhibits an order-of-magnitude improvement in stability compared to conventional phononic crystals, with minimal resonance shifts (~ 0.1%) even under 6% structural deformation. Our work establishes a crucial bridge between fundamental topological physics and practical devices, paving the way for topological signal processors while advancing phononic circuits, acoustoelectric integration, and AI-driven signal processing technologies.