Park Choon Mahn, Yim Geo-Su, Cho Kyuman, Lee Sang Hun
Department of Materials Physics, Dong-A University, Busan, 49315, South Korea.
Department of Electrical Engineering, Pai Chai University, Daejeon, 35345, South Korea.
Sci Rep. 2020 Nov 4;10(1):18991. doi: 10.1038/s41598-020-76111-4.
A two-dimensional (2D) slice of a 3D hemispherical acoustic Luneburg lens using a quasi-conformal transformation and face-centred-orifice-cubic (FCOC) unit cells is designed and fabricated. With the system, the focusing characteristics of acoustic waves with frequencies that satisfy the homogeneous medium condition of the metamaterial are observed, such as focusing of acoustic plane waves at the antipodal point on the transformed surface of the opposite side for the incident direction and focus spreading due to total internal reflection at the focus point. The attenuation losses of the system are measured and compared with those of an untransformed system with respect to frequency. The value of the acoustic Goos-Hänchen shift is determined by comparing the experimental and theoretical and simulated values of the focus points with respect to the incident angle. The effect of acoustic Fresnel filtering due to the angular distribution of the incident waves at the flat surface boundary is verified by comparing the results of the experiment and a simulation.
设计并制造了一种使用准共形变换和面心孔立方（FCOC）晶胞的三维半球形声学 Luneburg 透镜的二维切片。利用该系统，观察到了满足超材料均匀介质条件的频率的声波聚焦特性，例如，对于入射方向，声平面波在相对侧变换表面的对映点处聚焦，以及由于焦点处的全内反射导致的焦点扩展。测量了该系统的衰减损耗，并与未变换系统的衰减损耗随频率进行了比较。通过比较焦点相对于入射角的实验值、理论值和模拟值，确定了声学古斯 - 汉欣位移的值。通过比较实验结果和模拟结果，验证了由于平面表面边界处入射波的角度分布引起的声学菲涅耳滤波效应。
