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We study metamaterials with an anisotropic effective permittivity tensor in which one component is near zero. We find that such an anisotropic metamaterial can be used to control wave propagation and construct almost perfect bending waveguides with a high transmission rate (>95%). This interesting effect originates in the power flow redistribution by the surface waves on the input and output interfaces, which smoothly matches with the propagating modes inside the metamaterial waveguide. We also find that waves in such anisotropic epsilon-near-zero materials can be reflected by small-sized perfect magnetic conductor defects. Numerical calculations have been performed to confirm the above effects.The electromagnetic properties exhibited by metamaterials are remarkable. Indeed, they may provide almost arbitrary effective permeabilities and/or permittivities [1][2][3][4][5][6][7] . In previous studies on metamaterials, various interesting phenomena have been discovered, such as negative refraction 1 , perfect lens 3 , invisibility cloaks [4][5][6][7] , etc. Metamaterials with near zero parameters are also an important and intriguing class. Recently, epsilon-near-zero (ENZ) metamaterials with permittivity near zero, mu-near-zero (MNZ) metamaterials with permeability near zero, and index-near-zero (INZ) metamaterials with both permittivity and permeability near zero have been extensively studied and various applications have been proposed, such as directive emission devices [8][9][10][11][12] , creating subwavelength channels and bends [13][14][15][16][17][18][19] , tailoring the wave front 20,21 , realizing total transmissions and reflections in a channel by engineering defects [22][23][24][25] , bends designed through the principles of transformation optics [31][32][33][34] , and zero-index materials 13,[17][18][19] , etc. Silveirinha et al. 13 first proposed using isotropic epsilon-near-zero (IENZ) metamaterials to create subwavelength channels and bends, which was later experimentally realized by Liu et al. 17 and Edwards et al. 18,19 . However, in order to ensure high transmission, such isotropic channel is required to be very narrow in width.In this letter, we investigate the properties of anisotropic epsilon-near-zero (AENZ) metamaterials in which one component of the permittivity tensor is near zero. We find such a material can achieve almost perfect bending waveguides, which does not have the requirement of narrow channel width for high transmission. More interestingly, we can embed a small-sized perfect magnetic conductor (PMC) defect in the AENZ metamaterials to confine the wave propagation. It should be noted that with only one component near zero, such AENZ metamaterials are much easier to achieve than IENZ metamaterials in practice. Possible realizations of such AENZ metamaterials include metal-dielectric multilayered structures 35,36 , metal wire arrays 26,37 , etc. Before we study the bending waveguide of AENZ metamaterials, we first investigate the case of a straight waveguide. As illustrated in Fig....

We establish an account of electromagnetic scattering by coated spheres with radial dielectric and magnetic anisotropy. Within full-wave scattering theory, we show that the total scattering cross section Qs is strongly dependent on both the dielectric anisotropy and magnetic anisotropy. As a consequence, by a suitable adjustment of the radius ratio, one may make the anisotropic coated particle nearly transparent or invisible. In the quasistatic case, we take one step forward to derive the effective permittivity and permeability for the coated particle, and the near-zero scattering radius ratio can be well described within effective medium theory. To one's interest, the introduction of radial anisotropy is helpful to achieve better transparency quality such as a much smaller Qs and wider range of near-zero scattering ratio. Moreover, when the coated particle is anisotropic, the position of the near-zero scattering radius ratio can be tunable, resulting in a tunable electromagnetic cloaking.

We have developed a nonlinear differential effective dipole approximation (NDEDA), in an attempt to investigate the effective linear and third-order nonlinear susceptibility of composite media in which graded spherical inclusions with weak nonlinearity are randomly embedded in a linear host medium.Alternatively, based on a first-principles approach, we derived exactly the linear local field inside the graded particles having power-law dielectric gradation profiles. As a result, we obtain also the effective linear dielectric constant and third-order nonlinear susceptibility. Excellent agreement between the two methods is numerically demonstrated. As an application, we apply the NDEDA to investigate the surface plasma resonant effect on the optical absorption, optical nonlinearity enhancement, and figure of merit of metaldielectric composites. It is found that the presence of gradation in metal particles yields a broad resonant band in the optical region, and further enhances the figure of merit. PACS number(s): 77.22. Ej, 42.79.Ry, 77.84.Lf