使用无源线性超表面进行高效、高纯度的声音频率转换,Advanced Science

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使用无源线性超表面进行高效、高纯度的声音频率转换
Advanced Science ( IF 14.3 ) Pub Date : 2022-10-17 , DOI: 10.1002/advs.202203482
Wei Wang ₁ , Chengbo Hu ₁ , Jincheng Ni ₂ , Yujiang Ding ₁ , Jingkai Weng ₁ , Bin Liang ₁ , Cheng-Wei Qiu ₂ , Jian-Chun Cheng ₁

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尽管对波物理学和潜在应用具有重要意义，但传统的基于非线性的机制无法实现低频波的高效频率转换，其模式纯度、转换效率和两种光学器件中生成的谐波的实时可重构性都很差和声学。旋转多普勒效应提供了一种直观的范例来改变线性系统中的频率，然而，线性系统在波传播时需要螺旋相位变化。这里通过数值和实验方法展示了旋转被动线性涡旋超表面，在低至 3000 Hz 的可听声音频率中具有接近单位模式纯度 (>93%) 和高转换效率 (>65%)。传输声音的拓扑电荷几乎不受转速和透射率的影响，证明了原位调节高性能变频的机械鲁棒性和稳定性。这些特征使研究人员能够级联多个涡旋超表面，以进一步扩大和多样化声音频率转换的范围，这一点已经得到实验验证。该策略在声频域的随心所欲的声音操纵方面又向前迈进了一步，并且可能对各种声学通信、信号处理和非接触式检测产生深远的研究影响。

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Efficient and High-Purity Sound Frequency Conversion with a Passive Linear Metasurface

Despite the significance for wave physics and potential applications, high-efficiency frequency conversion of low-frequency waves cannot be achieved with conventional nonlinearity-based mechanisms with poor mode purity, conversion efficiency, and real-time reconfigurability of the generated harmonic waves in both optics and acoustics. Rotational Doppler effect provides an intuitive paradigm to shifting the frequency in a linear system which, however, needs a spiral-phase change upon the wave propagation. Here a rotating passive linear vortex metasurface is numerically and experimentally presented with close-to-unity mode purity (>93%) and high conversion efficiency (>65%) in audible sound frequency as low as 3000 Hz. The topological charge of the transmitted sound is almost immune from the rotational speed and transmissivity, demonstrating the mechanical robustness and stability in adjusting the high-performance frequency conversion in situ. These features enable the researchers to cascade multiple vortex metasurfaces to further enlarge and diversify the extent of sound frequency conversion, which are experimentally verified. This strategy takes a step further toward the freewheeling sound manipulation at acoustic frequency domain, and may have far-researching impacts in various acoustic communications, signal processing, and contactless detection.

更新日期：2022-10-17

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