| ABSTRACT: Metal optical elements with sub-wavelength structure have become a hot issue in recent years. This is due to the surface plasmon polaritons (SPPs) caused by the resonance between light and free electrons in metal, which leads to some amazing optical phenomenon such as high unusual transmission through nano-hole arrays, local field several hundreds even thousands times of incident light on metal surface, et al. At present, many optical devices with sub-wavelength based on SPPs have been developed as while as their physical mechanism are studied, and all kinds of photonic nano-devices based on SPPs are considered to be the basic of all-optical integrated loop with nanometer scale.In this thesis, scattering properties of a 2D rectangular metal cylinder and an unsymmetric finite metal grating are studied by boundary integral method (BIM), and the influence of fabrication errors is also investigated; a nano-cavity with subwavelength scale is designed, which can confine light in a region smaller than diffraction limit and the amplitude can reach to nearly a hundred times of incident light; the transmission properties of a slit with corrugations on both sides of a finite metal film is investigated, which show that the transmitted light is good bounded just as infinite films, and when the corrugation periods are changed from equal cycle to unequal cycle, the resonance peak corresponding to corrugations is split into several peaks which are related to the different corrugation periods. The details are as follows:1. The influence of fabrication flaws in experiments to the SPPs scattering properties of a rectangular metal cylinder is studied. We find that the flaws can make resonance peak blue-shifted, and the flaws greater, the shift larger. The scattering intensity is also weakened by the flaws.2. Near magnetic field distribution and electric field direction of a 2D metal film with unsymmetric corrugations on its surface are studied. Our simulation results show that when SPPs are excited, light energy is collected to one side of the film because of unsymmetric structure, which explained partly the high transmission of slit with corrugations. The influence of fabrication errors is also investigated, and we find that for such a large structure, the fabrication errors cause little influence to resonance wavelength, but the light intensity of resonance can be affected.3. A 2D nano-cavity built by two pieces of finite silver thin slabs with subwavelength corrugations on their inner boundaries is developed. The simulations show that it can confine light within diffraction limit, and the confined light spot is 1/5 of incident light in lateral direction and 1/20 in longitudinal direction. The amplitude of the strongest confined light reaches nearly 100 times of incident light. We also find that one can find the optimal parameters of the structure for achieving the maximal enhancement and confinement of the local field by various optimal algorithms.4. The transmission properties of a slit with corrugations on both sides of a finite metal film are studied. We find that the transmitted light is well bounded, just the same as that of the infinite films. Through analyzing the light intensity distribution, we deduce that two transmission peaks are corresponding to the corrugations period and the slit structure, separately, when the corrugation period is of equal periods. By changing geometric structure, we prove the correctness of our hypothesis. After changing the corrugation period to unequal periods, we find that the transmission peak corresponding to corrugation period are split into several peaks which are related to the different periods, respectively. |
PDF Full Text Request