Wave Propagation In Negative Refractive-Index Materials

Left -handed materials (LHM), of which the permittivity e and permeability μ are simultaneously negative, were first discussed theoretically by a Russian Physicist named Veselago V G in the 1968s. They have many strange properties such as negative phase velocity, negative refractive index, perfect imaging, inverse Doppler effect and abnormal Cerenkov radiation. But the exploration to it has been postponed, because naturally occurring materials with simultaneously negative permittivity s and permeability μ are not known. Recently, key experimental advances have been obtained, which make up negative refractive materials, so attracting more and more attention again. Though the theoretical analyses of LHM are interesting, there are some controversies, which include initially the causality of LHM in physics. For example, all previous theoretical predictions and experimental observations have been questioned by Valanju et,wherein the authors claim that the presence of dispersion prevents power transmitted at RHM-LHM interface from refracting at a negative angle, which means the refraction of group velocity n_g carrying the physics information isall along positive refraction, but "negative refractive material " means only the refraction of phase velocity np is negative. Furthermore, Pendry brought forward thatnegative refractive materials can enhance evanescent waves, even can make up perfect lens, which brings many argument.It is detailed that the causality of refractive theory in LHM by power propagation. Evanescent waves propagation in the presence of a layer of negative refractive material is studied, which of enhancement or decay regulation are analyzed, included power spread. The Goos-Haanchen shift is calculated when total internal reflection occurs at an interface between "normal" and negative refractive materials, and when a light beam travels through a slab of left-handed materials in the air, the lateral shift of the transmitted is discussed .Through our analytic calculation, we obtained several useful results.First, in part three, we have calculated the power flow of a wave transmitted from a nondispersive right handed materials into a dispersive left-handed materials. In particular, we have showed that negative refraction is possible for multifrequency signals by explicit calculation of the Poynting vector in LHM. Using two discrete frequencies, we have shown that the direction of time-averaged Poynting vector is in the average direction of the time-averaged Poynting vectors for each frequency treated separately, implying that negative refraction is possible. Using a Gaussian signal spectrum, we have confirmed this conclusion after also determining the power refraction angle to be negative, without violating causality. The angle of refraction was founded to be in agreement with that predicted by Snell's law, with the LHM having a negative index of refraction.Second, in part four, we have used the matrix formulation calculated the transmittance of multilayer structures that include LHM. The result shows a unusual photon tunneling through the combined LHM and RHM. (with the same magnitudes of refractive index and permeability ). When the thickness of the LHM and the RHM are matched, all the propagating waves also transmitted from the top simi-infinite medium to the bottom. Similar results are obtained for five-layer system when the LHM is sandwiched between two RHMS. But the impact of dispersive and absorption (losses) in LHM is grave. Our theoretically calculated result may have an impact on scanning photon tunneling spectroscopy and microscale the thermophotoltaic devise.Finally, in part five, we calculated the Goos-Haanchen shift at interface between RHM and LHM, which is negative consistent with the direction of energy flow in the negative refractive medium. But the lateral shift of the transmitted beam though a slab of LHM can be negative as well as positive by the stationary-phase approach. A necessary condition is put forward for the lateral shift and group delay to be positive, which is a restriction to the angle of incidence. The positive lateral shift also depends on the thickness of the slab, the negative refractive index. The relation of the lateral shift with its anomalous dependence on the thickness of the slab around resonances points is discussed. It's shown that the lateral shift of the reflected beam is equal to that of the transmitted beam when they are all measured from the normal to the interface (the x axis ) at which the incidence pointed is located. In order to demonstrate the validity of...