The Design And Mechanism Analysis Of Subwavelength Metallic Grating Filter

Ebbnsen found the transmission enhanced phenomenon on metal film with subwavelength holes array, which is a forefront research area in optical field. Although there are some debates about the physical mechanism of this phenomenon, an extensive attention has been paid on this area in a lot of fields, such as communication, biochemical sensors, new energy and medical detectors. Compared with the metal film with subwavelength holes array, the subwavelength metal grating has more simple structure. So the researchers prefer to subwavelength metal grating when they started to explore the mechanism of the transmission enhanced phenomenon. In addition, the subwavelength metal grating has polarization property because of its asymmetry. Currently, subwavelength metal grating has attracted a lot of interests in solar cells, filters, polarizations, lens, nano-imprinting and other fields, so it has promising applications.In this thesis, there are two main research aspects. One aspect is about exploring the physical mechanism of transmission extraordinary phenomenon of subwavelength metal grating. In this work, the influences of geometry parameters on single-layer subwavelength metal grating transmission were analyzed. The rules of extraordinary transmission were summarized. The extraordinary properties of transmission spectrum were explained based on surface Plasmon polarization and Fabry-Perot theory and the prediction method about the places of peak and valley in spectrum were proposed. Furthermore, the mechanism of the model of two-layer subwavelength metal grating which requires simple fabrication technology was analyzed. The resonance modes of its transmission peaks in spectrum were discussed. Also, the distinction and likeness of single-layer and double-layer subwavelength metal grating was compared.Another aspect is about designing two novel polarizing filters based on subwavelength metal grating utilizing Finite Different Time Domain (FDTD) method. One is the thriple-layer (metal-dielectrici-metal) grating filter. In this work, the influences of dielectric grating layer on transmission spectrum and its mechanism were analyzed. In contrast to single-layer grating, this filter has narrower band filtering effect in visible light. The other is the subwavelength metal grating with grooves. In this work, the resonance mode and the influence of the groove was discussed. The peak position of transmission spectrum can be tuned through changing the geometry parameters. So three color (red, green and blue) filters were designed based on this structure and the designed method was introduced. The transmission of the designed color filters is more than65%, and the extinction ratio is more than40.