Yang Suxia, Page J H, Liu Zhengyou, Cowan M L, Chan C T, Sheng Ping
Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2.
Phys Rev Lett. 2004 Jul 9;93(2):024301. doi: 10.1103/PhysRevLett.93.024301. Epub 2004 Jul 7.
We present a combined experimental and theoretical study of phonon focusing phenomena in a pass band above the complete band gap in a 3D phononic crystal. Wave propagation was found to depend dramatically on both frequency and incident direction. This propagation anisotropy leads to very large negative refraction, which can be used to focus a diverging ultrasonic beam into a narrow focal spot with a large focal depth. The experimental field patterns are well explained using a Fourier imaging technique, based on the 3D equifrequency surfaces calculated from multiple scattering theory.
我们展示了对三维声子晶体中完全带隙之上通带内声子聚焦现象的实验与理论相结合的研究。发现波的传播强烈依赖于频率和入射方向。这种传播各向异性导致了非常大的负折射，可用于将发散的超声束聚焦到具有大焦深的狭窄焦点处。基于多重散射理论计算出的三维等频面，利用傅里叶成像技术可以很好地解释实验场模式。
