Nondispersive One-Way Signal Amplification in Sonic Metamaterials
Nondispersive One-Way Signal Amplification in Sonic Metamaterials
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DOI：
10.1103/physrevapplied.17.024020
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发表时间：
2021-10
影响因子：
4.6
通讯作者：
Noah Kruss;J. Paulose
中科院分区：
文献类型：
--
作者：
Noah Kruss;J. Paulose
参数放大-通过系统参数的周期性调制将能量注入波-通常限于调制频率的特定倍数。然而，宽带参量放大可以在有源超材料中实现，其允许局部参数在空间和时间上都被调制。受光学中的腔超材料概念的启发，我们描述了一种使用行波形式的局部刚度的时空周期调制在整个频带上单向放大声波的机制。当调制波的速度接近超材料中的声速时--一种称为声波极限的状态--几乎所有正向传播的声波带中的模式都被放大，而反向传播带中没有放大。为了消除连续材料中声波极限固有的发散，我们使用精确的Floquet-Bloch方法来计算离散周期系统的动态激发带。我们发现宽范围的参数，放大在最低频段几乎是均匀的，使波包放大，同时保持其速度，形状和频谱内容。我们的机制提供了一种设计声学超材料的途径，这种材料可以在很宽的频率范围内无损耗或失真地传播波脉冲。
Parametric amplification -- injecting energy into waves via periodic modulation of system parameters -- is typically restricted to specific multiples of the modulation frequency. However, broadband parametric amplification can be achieved in active metamaterials which allow local parameters to be modulated both in space and in time. Inspired by the concept of luminal metamaterials in optics, we describe a mechanism for one-way amplification of sound waves across an entire frequency band using spacetime-periodic modulation of local stiffnesses in the form of a traveling wave. When the speed of the modulation wave approaches that of the speed of sound in the metamaterial -- a regime called the sonic limit -- nearly all modes in the forward-propagating acoustic band are amplified, whereas no amplification occurs in the reverse-propagating band. To eliminate divergences that are inherent to the sonic limit in continuum materials, we use an exact Floquet-Bloch approach to compute the dynamic excitation bands of discrete periodic systems. We find wide ranges of parameters for which the amplification is nearly uniform across the lowest-frequency band, enabling amplification of wavepackets while preserving their speed, shape, and spectral content. Our mechanism provides a route to designing acoustic metamaterials which can propagate wave pulses without losses or distortion across a wide range of frequencies.