Research Of Optical Characterization Of Negative Metamaterial

In the classic "optical" of the giants in science—Isaac Newton, he studied thelight’s refraction, transmission, reflection, and color in detail. Since then, people areused to using the refractive index as a material property to describe the direction of lightpropagation. With a deep understanding of electromagnetic wave, people found therefractive index can describe more things besides light direction. It also expressed thelight velocity in the material, permittivity and permeability.In1968, Veselago discovered that there is possibility that the refractive index benegative based on theoretically research the analytic expression, and proposed theconcept of negative refraction material. Then people imagined the application ofnegative refraction materials, such as perfect lens, making cloak material and so on. Butthere isn’t any negative refraction material in nature, and its study was confined totheoretical exploration only. About2000, Pendry and Dr Smith, manufactured andtested the artificial metamaterial in microwave frequencies. And the study became atheoretical and experimental basis for later research.In this paper, the design of negative refraction materials is based on the goldnanowire array. Including the theory of plasma, surface plasma wave excitation mode,etc., simulation model, optimization, near-field optical experimental characterization ofeach project has been studied. We are aim to design and manufacture the artificialnegative refraction material under the current processing technology, and then takeoptical experimental characterization methods to research it. Traditional experiment waslimited in precision of equipment and various aspects factor, so most researches wereonly approached theoretically or in computer simulations. In this paper, the NSOMcharacterization method is simple and clear. Combined with the simulation results, thenegative refraction phenomenon were clearly and legibly described, which is differentfrom the previous experimental studies. Numbers of difficult problems in testing havebeen solved.Firstly we investigated the structure parameters and manufacturing error whichmay affect the performance of negative refraction using FDTD algorithm. Optimize the performance in computer simulations. Through the simulation results, it shows the lightsource wavelength, radius of the nanowires and structure period are main factorsinfluencing the electromagnetic response. Nanounits spacing, arrangement of lattice,surface roughness and so on had no significant effect on the distribution of light. Finallywe derived the optimized parameters: golden nanowires radius of about100nm, period400nm, and excitation light source wavelength532nm. This set of model performedthe most remarkable negative refraction phenomenon.At last, we experimentally tested the sample and normal material using light sourceof532nm, and compared their vertical light distribution. A focus has been observedbeyond sample, which is a special phenomenon of negative material under diverginglight source. The test results agree with designed light path, provided an evidence of thesample to be negative material.