Propagation Of Electromagnetic Waves In Double-negative And Single-negative Materials

Double-negative material is such a kind of medium of which the permittivity and permeability are simultaneously negative. This material is often called as left-handed material because the electric field ( E|(?) ), the magnetic field ( H|(?) ) and the wave vector ( k|(?) ) of the electromagnetic waves propagating in this material obey the left-handed rule. On the contrary, the material with both positive permittivity and positive permeability is called as right-handed material because the electric field ( E|(?) ), the magnetic field ( H(?) ) and the wave vector ( k|(?) ) of the electromagnetic waves propagating in this material obey the right-handed rule. Different from double-negative material, single-negative material is such a kind of medium that its permittivity or permeability is negative and the other is positive. If the permeability is negative and the permittivity is positive, this kind of single-negative material is called as magnetic-negative material. Correspondingly, if the permittivity is negative and the permeability is positive, this kind of single-negative material is called as dielectric-negative material . We focus our attention on the transmission properties of the electromagnetic waves propagating in double-negative material and single-negative material. Our main work is listed as follows 1. The equivalence between double-negative layer and the bilayer made of magnetic-negative and dielectric-negative materials In the limit of the long wavelength, by using transfer matrix method, we present the explicit expressions for the effective permittivity and permeability of the bilayer made of magnetic-negative layer and dielectric-negative layer. Numerical results show that the bilayer can be equivalent to double-negative layer because its effective permittivity and permeability can be negative simultaneously in certain range of frequency. We also show that, like double-negative layer, the bilayer can also amplify evanescent waves owing to the excitation of the surface polaritons at the interfaces between layers, which further confirms the equivalence. 2. Band gap of one-dimensional photonic crystal containing double-negative material or single-negative material Under effective medium approximation, we study the zero volume averaged refractive index gap in the one-dimensional photonic crystal consisting of double-negative material and right-handed material, and the zero effective phase shift gap in the one-dimensional photonic crystal consisting of magnetic-negative material and dielectric-negative material. We find that the two photonic band gaps can be well explained through the total reflection. Furthermore, within effective medium approximation, we can easily understand some important properties on these gaps, such as the invariance of scale length, that is, the position and width of photonic band gap are invariant with a change of scale length. 3. Near-field imaging by the multi-layer made of double-negative material and right-handed material Using transfer matrix method, we investigate the amplitude recovery and phase shift of near-field which is emitted from an object and then transmitted from the object plane to the image plane by the multi-layer made of double-negative material and right-handed material. We find that, in comparison with a single double-negative slab, the multi-layer can decrease the influences of the dispersiveness and absorption of double-negative material on near-field imaging, because it can restore more high-frequency information of an object at imaging plane due to the excitation of more surface polaritons, and therefore increase greatly the special resolution of the image. Moreover, in the case that dispersiveness and absorption coexist, we find that proper absorption may decrease the influence of dispersiveness on near-field imaging, because it can suppress the excess amplification of near field owning to dispersiveness and thus prevent the image from distortion.