Devaux T, Tozawa H, Otsuka P H, Mezil S, Tomoda M, Matsuda O, Bok E, Lee S H, Wright O B
Division of Applied Physics, Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan.
Institute of Physics and Applied Physics, Yonsei University, Seoul 03722, Republic of Korea.
Sci Adv. 2020 Mar 6;6(10):eaay8507. doi: 10.1126/sciadv.aay8507. eCollection 2020 Mar.
Wave concentration beyond the diffraction limit by transmission through subwavelength structures has proved to be a milestone in high-resolution imaging. Here, we show that a sound wave incident inside a solid over a diameter of 110 nm can be squeezed through a resonant meta-atom consisting of a nanowire with a diameter of 5 nm equal to λ/23, where λ is the incident acoustic wavelength, corresponding to a transmission efficiency of 500 or an energy densification of ~14,000. This remarkable level of extraordinary acoustic transmission is achieved in the absence of ultrasonic attenuation by connecting a tungsten nanowire between two tungsten blocks, the block on the input side being furnished with concentric grooves. We also demonstrate that these "solid organ pipes" exhibit Rayleigh end corrections to their effective longitudinal resonant lengths notably larger than their in-air analogs. Grooves on the output side lead to in-solid directed acoustic beams, important for nanosensing.
通过亚波长结构传输实现超越衍射极限的波聚焦，已被证明是高分辨率成像领域的一个里程碑。在此，我们展示了一种直径为110纳米的固体内部入射的声波，能够通过一个由直径为5纳米（等于λ/23，其中λ为入射声波波长）的纳米线构成的共振元原子进行压缩，这对应着500的传输效率或约14,000的能量致密化。通过在两个钨块之间连接一根钨纳米线实现了这种非凡的超声传输，且不存在超声衰减，输入侧的钨块设有同心凹槽。我们还证明，这些“固体风琴管”对其有效纵向共振长度表现出瑞利末端修正，明显大于其在空气中的类似物。输出侧的凹槽导致固体中的定向声束，这对纳米传感很重要。
