Frequency-Multiplexed Transmitted-Wave Manipulation with Multifunctional Acoustic Metasurfaces

Passive metasurfaces are known for their fixed and usually single-wave manipulation functionality, which limits their potential applications for diverse scenarios. To expand the functionality of the passive metasurfaces, frequency-multiplexed technology has been proposed to encode multiple operation frequencies in a single metasurface for function selection and switching. Although this technology has been extensively utilized for electromagnetic waves, there have been few studies on designing frequency-multiplexed metasurfaces for acoustic-wave manipulation. This work applies a topology optimization method based on a multiobjective genetic algorithm (GA) to develop different frequency-encoded multifunctional acoustic metasurfaces to attain acoustic focusing and anomalous wave refraction. The effectiveness of the optimized metasurfaces is validated both numerically and experimentally. Additionally, the underlying physical mechanisms of the designed frequency-multiplexed acoustic metasurfaces are systematically analyzed. This study presents high-performance frequency-multiplexed metasurfaces for acoustic-wave-front modulation and demonstrates the promising potential of the GA-based topology optimization approach in designing integrated, miniaturized multifunctional acoustic devices for real-world applications.