Left-handed Materials, The Study Of Polarization

The left-handed material (LHM) is an artificial composite material with simultaneously negative permittivity and negative permeability. For electromagnetic waves propagating in such materials, the electric field E, magnetic field H and wave vector k form a left-handed triplet of vectors and so such materials are called LHMs. LHMs exhibit many unique electromagnetic properties, among which the most well-known is negative refraction. So, LHMs are also called as negative-index materials. Other properties include reversed Doppler effects, reversed Cherenkov radiation, and so on. Electromagnetic wave incidents on a planar interface between a regular material and a LHM will undergo negative refraction. Hence a LHM planar slab can act as a lens and focus waves from a point source. Furthermore, a LHM slab can amplify evanescent waves and thus behaves like a perfect lens. The amplitudes of evanescent waves from a near-field object could be restored at its image. Therefore, the spatial resolution of the superlens can overcome the diffraction limit of conventional imaging systems and reach the sub-wave length scale. After the first realization in 2001, LHMs and negative refraction have been the hot topic in physics, optics, materials, and electronics and so on in the word.Firstly, this thesis investigates the reflective and refractive characteristics of electromagnetic wave at the interface between vacuum and left-handed material. The amplitude, polarization, and phase of reflective and refractive waves are discussed. Our results show that left-handed material can be divided into two classes according to its permittivityεand permeabilityμ.They have different Brewster's angles and different polarization characteristics of reflection wave. The influences of the left-handed materials withεμ> 1andεμ< 1 on the phases of reflective waves are studied. The comparison between the right-hand material and the left-handed material is given.Then, the reflected intensity and the degree of polarization of reflected wave at interface between left-handed material and vacuum have been studied. Our results show that the reflectivity depends on the incident angle, the permittivityεand permeabilityμ. If the permittivityεand permeabilityμare interchanged, the parallel reflectivity and the vertical reflectivity are also interchanged. For two kinds of LHMs, Brewster's angle reduces as the refractive index increasing atμ>εwhile Brewster's angle increases as the refractive index reducing.Finally, we focus on the reflective and refractive characteristics of the uniaxially anisotropic LHMs. Studies show that, at the interface between the uniaxially anisotropic left-handed material and vacuum, an odd total reflection can happen under the condition of the incident angle smaller than the critical angle. The polarization phenomenon is also interesting when the electromagnetic wave incidents at the interface of the vacuum and the uniaxially anisotropic LHM or at that of two kinds of uniaxially anisotropic LHMs. Its Brewster angle is more complicated. It depends on not only the parameters of the materials but also the frequency of incident wave. It is shown that the propagation characteristic of electromagnetic wave in uniaxially anisotropic LHMs is quite different from that in isotropic LHMs.