单轴晶体中的负折射现象研究

Investigation of Negative Refraction in a Uniaxial Crystal

分析了在各向同性介质和单轴晶体界面实现负折射的最佳条件。计算发现,通过调节光轴角和各向异性参量可以使得负折射现象更为明显,获得最佳光轴角和最大入射临界角。各向异性强的晶体实现负折射的入射角范围可能会很大。讨论了单轴晶体中和负折射率介质中的负折射现象的区别:负折射率介质中的负折射是由负的折射率引起的,单轴晶体中是由于各向异性决定的。同时还发现单轴晶体中的能流负折射现象不能实现Pendry在理论上所预言的完美透镜。

By relying on dispersion equation, optimal conditions for negative refraction in the interface between isotropic medium and anisotropic crystal are investigated, The negative refraction phenomenon can be very evident when the optical axial angle and anisotropic parameters are arranged appropriately, The optimal optical axis angle and corresponding maximum incident critical angle are given. For strong anisotropy crystal, the maximum incident angle that yields the negative refraction could be very large. Further, the difference of negative refraction associated with uniaxial crystal and with negative index media is discussed. In negative index media the negative refraction is caused by a negative refractive index, whereas in the case of anisotropic crystal, the negative refraction is a natural result of dispersion relation in anisotropic media. It is found that the uniaxial crystal slab is not suitable for constructing perfect lens, firstly predicted by Pendry.