Optical Properties Of Periodic Slit-groove And Electromagnetically Induced Transparency In Metamaterials

With the development of technology in the past decade, the micro structure materials (metamaterials) can be fabricated by many methods. Novel optical properties of the metamaterial have been demonstrated due to the strong interaction between the electromagnetic waves and the materials, which offers a tool to design microstructures with the expected properties, such as electromagnetically induced transparency, stealth, the transmission enhancement, negative refraction etc. Thus the field attracts researchers from various areas.The optical transmission properties of some specially designed metamaterials (1D periodic array of slit-grooves, periodic array of SRR and nanorod pair as well as sandwich structure) are studied in the thesis.The main results are as follows:1. The optical transmission properties of the periodic array of slit-groove are experimental and theoretical studied. The results show that the groove depth and location have an important effect on the transmission spectrum. While the variation of the groove depth and location has little influence on the transmission peak, the dip is very sensitive to these changes, especially the groove depth. With the increase of the groove depth, the dip is red-shifted greatly, showing an exponential relationship. In order to understand the physical mechanism of the transmission characteristic, the phenomenological model and the coupled-wave model have been used to treat the problem analytically. The results are in good agreement with each other, also in good agreement with the simulation and the experiment. The advantage of the phenomenological model lies in its clear physical picture and that of the coupled-wave model gives a rigorous mathematical result.2. In order to realize double electromagnetically induced transparency, a planar metamaterial composed of split-ring resonators (SRR) and nanorods has been studied numerically. The EIT appears whether the polarization of the incident light is in the x direction or in the y direction. The simulations reveal that when the attracting interaction between the SRR and the bar is increased the corresponding peak or valley is red-shifted; while when the repulsive interaction becomes stronger the corresponding peak or valley is blue-shifted. The mechanism of the two is different. For the x polarization, the appearance of the EIT is due the the bright mode-dark mode coupling. For the y polarization, it is due to the bright mode-bright mode coupling. The behavior of these two types EIT responses differently to the changes of the parameters.3. We also studied the double EIT in a sandwich structure, which is made of metal nanorods-media-metal nanorods, that is, a three layered structure. The nanorods in the lower layer are arranged horizontally while the nanorods in the upper layer vertically. It is shown that the EIT is mainly due to the layer with its nanorods parallel to the electric field. And the coupling between the lower and upper layer also plays some role in the transmission spectrum. The structure provides more freedom for the design.