Negative birefraction of acoustic waves in a sonic crystal
Negative birefraction of acoustic waves in a sonic crystal
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声波晶体中声波的负双折射
DOI：
10.1038/nmat1987
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发表时间：
2007-10-01
期刊：
影响因子：
41.2
通讯作者：
Ming, Nai-Ben
中科院分区：
文献类型：
--
作者：
Lu, Ming-Hui;Zhang, Chao;Ming, Nai-Ben
光学双折射和二向色性是由各向异性晶体中两个独立的光波偏振引起的经典而重要的效应(1)。此外，光子晶体中横向电波和横向磁极化电磁波的明显色散关系更容易导致双折射(2-6)。然而，流体中的声波不可能表现出这样的双折射，因为只有纵模存在。人造声波晶体(SC)的出现极大地拓宽了自然界中可产生声波带隙并用于控制声波传播的声学材料的范围(7-18)。近年来，负折射引起了人们的广泛关注，并在左手材料和光子晶体中得到了证实(19-26)。与左手材料和光子晶体类似，在SC 14-18中也发现了负折射。在这里，我们首次报道了二维SC中的声学负双折射现象，即使在相同的频率和相同的偏振状态下也是如此。利用这一特点，实现了点源的双聚焦成像。这种双折射概念可以推广到与其他形式的波相对应的其他周期系统，这对基础物理和器件应用都有很大的影响。
Optical birefringence and dichroism are classical and important effects originating from two independent polarizations of optical waves in anisotropic crystals(1). Furthermore, the distinct dispersion relations of transverse electric and transverse magnetic polarized electromagnetic waves in photonic crystals can lead to birefringence more easily(2-6). However, it is impossible for acoustic waves in the fluid to show such a birefringence because only the longitudinal mode exists. The emergence of an artificial sonic crystal (SC) has significantly broadened the range of acoustic materials in nature(7-18) that can give rise to acoustic bandgaps and be used to control the propagation of acoustic waves. Recently, negative refraction has attracted a lot of attention and has been demonstrated in both left-handed materials and photonic crystals(19-26). Similar to left-handed materials and photonic crystals, negative refractions have also been found in SCs14-18. Here we report, for the first time, the acoustic negative-birefraction phenomenon in a two-dimensional SC, even with the same frequency and the same 'polarization' state. By means of this feature, double focusing images of a point source have been realized. This birefraction concept may be extended to other periodic systems corresponding to other forms of waves, showing great impacts on both fundamental physics and device applications.