Microwave Left-handed Materials, Negative Refraction Effect, Their Defective Regulation

Left-handed metamaterials (LHMs) are characterized by a negative effective permittivity and simultaneously a negative effective permeability, and it is named by the propagation of electromagnetic waves in matter that electric field E , magnetic field B and wave vector K content with left-handed rule. Present a variety of unusual electromagnetic and optical properties, such as reversed Doppler shift, Cherenkov radiation, Goos-Hanchen shift, negative refraction effect and perfect lens. In 1968,Veselago introduced the concept of Left-handed metamaterials, but nearly about 30 years, no known materials exist in nature with simultaneously negative ε and μ both negative have remained a curious exercise in electromagnetic theory .However, Pendry et al. suggested a model of periodic array on this metallic wires to simulate plasma and obtained a negative ￡ below the plasma frequency. An array of split ring resonators (SRRs) was adopted to realize a negative μ .at the region close to the resonance frequency. By combining SRRs and wires, Smith and his collaborators first demonstrated the negative index of refraction of LHMs. The discovery of Left-handed material has been regarded as one of the ten most significant discoveries in science community in 2003. The structure of left-handed metamaterials in infrared and visible light is micron and nanometer, so it is very important to study defect in LHMs.In this paper, we have investigated the defect effect on negative refraction of the LHMs in a planar slab waveguide. The printed circuit boards with LHMs are fabricated using a shadow mask/etching technique. The experimental results show that when the defects are introduced into the sample, the negative refraction index and the max power have changed. In addition, we also experimentally investigated the microwave reflection of the negative permeability material composed of periodically arrays of the copper SRRs, the negative dielectric materials composed of periodically arrays the copperwires and the LHMs when microwave is incident to the surface with different direction. We have got the results below.1. We have investigated LHMs when microwave is incident to the surface with different direction. We can get the results below:(1) For the negative permeability materials, there is a reflection peak at the resonance frequencies of the SRRs;(2) The reflectivity of the negative dielectric material is closed to OdB;(3) A single reflection peak with lower depth occurs in the reflected curve of the LHMs, the depth of reflection peak decreases with the incident direction, that is, reflection increases. The reflection peak has a shift with respect to the transmission peak;(4) It is demonstrated that negative refractive index of-0.796 occurs in the LHMs at the frequency of 9800MHz.2. We have investigated the defect effect on negative refraction of the LHMs. It leads to the changes of the negative refraction index and the max power. So we can control the negative refraction index of LHMs. We can get the experimentally results below:(1) when two kinds of point defects are introduced into the sample, the ratio of the max power with point defects to without defects are 1.035 and 1.256 , and the absolute value of the negative refraction index increases by 9.6 % and 19.6 %, respectively;(2) When three kinds of vacant defects are introduced into the sample, the ratio of the max power with vacant defects to without defects is 1.973 at most and 0.364 at least, the absolute value of the negative refraction index has increased by 68.33 % at most and 9.6 % at least .The different vacant defects break the symmetry of perfect LHMs and result in a new electromagnetic resonance.