Guided Mode Resonance And Extraordinary Transmission In Subwavelength Metallic Gratings

With the development of the micro and nano-optics, artificial subwavelength microstructures have gained much attention due to several special optical properties and controlling methods beyond the ordinary ones. The dimension of the subwavelength microstructure is mainly of the wavelength scale, which can be used to make those microstructure as the high transmittance component, filters and polarizing- splitter leading to a new stage for the optical on-chip interconnects. For the subwavelength structure, the optical effects cannot be simply explained by traditional optics, demanding a quantum-optical analogy. The diffraction property of subwavelength metallic gratings can show special optical properties, such as guided mode resonance and extraordinary transmission enabling potential application in the refractive-index sensing, narrow line filtering and so on.In the thesis, we develop and implement a theoretical method based the rigorous coupled wave approximation(RCWA), in order to understand the microscale-interaction mechanisms of the optical filed. For the special properties of subwavelength metallic gratings, the ordinary RCWA has been improved. Comparable results have been obtained by the RCWA and the finite element full-wave simulation.Ordinary rigorous coupled theory focused on the dielectric gratings, we improve it and implement a package, which runs fast, showing good convergence and stability, and can be used to analyze the fundamental diffraction properties of the nano metallic gratings. By examining the diffraction spectrums, it is shown that there are just zero-order and first-order diffraction whose diffraction efficiency had great effect on the parameter values.By modeling the grating as a periodic waveguide, the optical resonance properties of the grating can be analysed, It is shown that guide mode resonance dominates in such structures. Extraordinary transmission can be found and explained based on the RCWA. In view of that, based on the Fabry-Perot resonance and surface plasmion polartion, we have designed a kind of double-layer-metallic gratings and bi-metallic double metallic gratings. By examining the transmitted spectrum and the eigenmodes, we analyzed the resonance optical transmission in terms of guide mode resonance. For these properties, we propose possible applications based on such metallic gratings.In the paper, the results for understanding the resonance modes and enhanced transmission on the micro-nano multilayer period and non-period structure have important theroetical significance, and provide a complete calculation method and program. Except, relevant results can be used to design optical sensers, broadband or ultra-narrow-band gratings.