Yan Wei, Yan Min, Qiu Min
Laboratory of Optics, Photonics and Quantum Electronics, Department of Microelectronics and Applied Physics, Royal Institute of Technology (KTH), Electrum 229, 16440 Kista, Sweden.
J Opt Soc Am A Opt Image Sci Vis. 2011 Jun 1;28(6):1058-66. doi: 10.1364/JOSAA.28.001058.
A type of transformation media called α media is proposed by performing a direct transformation to the metric tensor of another kind of media, called seed media. Light rays in an α medium correlate to those in its seed medium through a simple displacement or rotation relation. Three types of commonly encountered anisotropic media are covered by the concept of α media: (1) media of slab shape, having continuous translational symmetry with respect to two Cartesian coordinate components; (2) media of cylindrical shape, having cylindrical rotational symmetry and continuous translational symmetry along the longitudinal direction; (3) media of spherical shape, having spherical rotational symmetry, with two principal axes along the symmetry directions, and with the material parameters in the same sign. Optical properties of such media can be effectively interpreted through recalling the properties of certain isotropic media, i.e., their seed media. Conversely, from simple isotropic media in which light trajectories are well known, one can design α media for manipulating light. Based on this fact, several optical devices, including frequency demultiplexers, beam splitters, focusing lenses, and radiation controllers, are designed and numerically verified. The famed invisibility cloak derived from a conventional coordinate transformation is revisited from the α media perspective.
通过对另一种称为种子介质的介质的度规张量进行直接变换，提出了一种称为α介质的变换介质类型。α介质中的光线通过简单的位移或旋转关系与其种子介质中的光线相关联。α介质的概念涵盖了三种常见的各向异性介质：（1）平板形状的介质，相对于两个笛卡尔坐标分量具有连续的平移对称性；（2）圆柱形状的介质，具有圆柱旋转对称性并沿纵向具有连续的平移对称性；（3）球形介质，具有球旋转对称性，两个主轴沿对称方向，且材料参数符号相同。通过回顾某些各向同性介质（即它们的种子介质）的特性，可以有效地解释此类介质的光学特性。相反，从光线轨迹已知的简单各向同性介质出发，可以设计用于操控光的α介质。基于这一事实，设计了包括频率解复用器、分束器、聚焦透镜和辐射控制器在内的几种光学器件，并进行了数值验证。从α介质的角度重新审视了源自传统坐标变换的著名隐形斗篷。
