Acoustic backward-wave negative refractions in the second band of a sonic crystal.
Acoustic negative refractions with backward-wave (BW) effects were both theoretically and experimentally established in the second band of a two-dimensional (2D) triangular sonic crystal (SC). Intense Bragg scatterings result in the extreme deformation of the second band equifrequency surface (EFS) into two classes: one around the K point and the other around the point of the reduced Brillouin zone. The two classes can lead to BW negative refractions (BWNRs) but with reverse negative refraction dependences on frequencies and incident angles. Not only BWNR but BW positive refraction can be present at EFSs around the K point, so it is possible to enhance the resolution of acoustic waves with a subdiffraction limit regardless of refractions, which is no analogy in both left-handed material and SCs' first band. These abundant characters make refractions in the second band distinguished.
Feng
Liang
L
National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China.
Liu
Xiao-Ping
XP
Lu
Ming-Hui
MH
Chen
Yan-Bin
YB
Chen
Yan-Feng
YF
Mao
Yi-Wei
YW
Zi
Jian
J
Zhu
Yong-Yuan
YY
Zhu
Shi-Ning
SN
Ming
Nai-Ben
NB