Investigation Of Light Transmission Through The Structures Composed Of Dispersive Materials

Recently, the special properties of the micro- or nano-structures fabricated fromthe dispersive materials have attached increasing attentions. For example, the trans-mission of light through the metallic subwavelength hole array is 2-3 order higher thanthe hole porosity. The one-dimensional photonic crystal constructed by stacking alter-native layers of positive and negative index materials can present a new type of bandgap which is immune from the random thickness error and insensitive to the polar-ization and angle of incidence. These new phenomena provide novel approaches forfabrications of photoelectric devices with nanometer scale. Furthermore, the phys-ical mechanism for these phenomena has not been clearly explained. Motivated bythese problems, the transmission and absorption property of the longitude and latitudestructure fabricated from the dispersive materials have been investigated. The majorachievements made in this thesis are summarized as follows:The transmission property of the slit array is investigated by using the two-dimensional finite difference of time domain (FDTD) method. Two models are con-structed to show the dependence of the transmission spectrum on the slits structure.The sandwiched structure is used to exhibit the contribution of the metallic wall in-side slits to the extraordinary high transmission. A filled slits structure is employed toshow the relation between the average refractive index inside slits and the transmis-sion spectrum of the structure. The obtained results can be explained well with thewaveguide resonance theory.The transmission characteristic of a metallic film with subwavelength periodicsquare hole arrays is investigated by using the three-dimensional FDTD method. Thein?uences of the holes size, the refractive index of substrate, the refractive index offilled medium and the thickness of film as well as the incident angle on the charactersof transmission spectra are studied. It is found that the transmission can be furtherenhanced by filling the holes with higher refractive index medium. Because fillingthe hole, on the one hand, increases the effective size of hole and results in furthertransmission; on the other hand, the cut-off wavelength of waveguide mode increases,therefore, the waveguide mode is red-shifted and be moved into the surface plasmon resonance region. Thus the transmission is enhanced by the collaboration of localizedwaveguide resonance with surface plasmon resonance.The optical re?ectance of a thick metallic plate arranged with subwavelengthsquare hole array is investigated. There are few dips in the re?ectivity spectra, whichindicate the absorption peaks. The absorption peaks behave differently according tothe ratio of holes width, the period of the holes and the depth. Combining with the nearfields of the absorption peaks, it is also found that the surface plasmon resonance onthe surface of plate and localized surface plasmon in holes lead different absorptionsmodes.Four kinds of one dimensional photonic crystals (1DPCs) composed of disper-sive materials (including negative refractive index materials, negativeμmaterials,negative materials and positive refractive index materials) are proposed. The de-pendence of the band gaps on the angle of incidence and thickness scale are investi-gated by using the transfer matrix method. Simulation results show that the band gapsof these dispersive material 1DPCs are insensitive to the thickness scale. The defectmodes of these doped 1DPCs behave specially when the thickness of the defect layer,the angle of incidence and the thickness scale of PC change. The characters of theband gaps of these photonic crystals and defect modes of doped photonic crystal aredifferent from that of usual photonic crystals.