In this thesis, we have investigated the transmittance of one-dimensional(1D) and three-dimensional(3D) metallo-dielectric photonic crystals(MDPC). We calcualted the transmittance of a one-dimensional metallo-dielectric photonic crystal in the optical region including the absorption losses in metal layers. The structure consists of five layers of Ag and six layers of GaN. The layer thickness of Ag is 30 nm, and that of GaN 64 nm. Although the total thickness of Ag in 1D MDPC is several times larger than the skin depth, about 15 nm in the optical region, the transmittance is larger than that of bulk layer and is changed little when the GaN layer is replaced with other dielectric materials like MgF_2, ZnO and ZnS.
When we change the thickness of dielectric layer at the end of the stack for a half-thickness of other layer, the transmittance of the MDPC is increased twice as much and the oscillations in the transmission spectrum are also smoothed out compared with the case without them. These half-thick layers play the role of antireflection coating. But the thickness value of these dielectric layers is different from either λ/2 or λ/4, as the phase shift induced by the reflection at the dielectric-metal interfaces is neither 0 nor π. The enhancement of transmittance is strongly dependent on the dielectric constant of dielectric layer, while it is not affected by that of the metal. The transmittance is maximum when the refractive index of dielectric material and the imaginary part of refractive index of the metal layer have the same value. For obliquely incident waves, the transmittance is also increased and the transmission spectrum became much smoother compared with the case without the half-thick dielectric layers. The shift of the center wavelength of the transmission band for oblique incidences toward the shorter wavelength is larger for the TE modes than for the TM modes, because the effective refractive index of metal layers is smaller for the TE modes than for the TM modes. This MDPC is conductive and transparent in the visible range, blocking ultraviolet and infrared light, so it can be used for sensor protections, UV protective films and transparent conductive display panels. The enhancement of optical transmission by changing the thickness of dielectric layer at the end of the stack for the half-thickness is very important in improving the performance of the above mentioned devices.
We also investigate the band gap structure of photonic crystals composed of silver spheres. Any periodic structure assembled with metal spheres have complete photonic band gaps. Therefore theoretical analysis about the photonic crystal with metal spheres is important to make the complete photonic band gaps. First, we calculate the transmittance of monolayers for both square and triangular array of spheres when the distance between spheres is very large compared with the radius of sphere. In each case a dip exists in the transmittance spectrum at the wavelength of 353 nm when the real part of dielectric constant of silver is -2. It is because localized surface modes are excited around the silver surfaces. When the spheres get closer, the mode for this dip splits into two modes because of the coupling between the localized surface modes. In a 3D photonic crystal made by stacking monolayers, additional band gap is generated due to the periodicity along the propagation direction of the electrical field. The depth, width and position of this gap are dependent on the distance between the monolayers, while the gap originated by the surface modes of spheres is not affected.
