Surface plasmon polaritons (SPPs), which are waves propagating along a metal-dielectric interface with an exponentially decaying field in both sides, have been considered as a promising way to overcome the classical diffraction limits of optical devices. Subsequently, sizes of optical devices are greatly miniaturized by taking advantages of functionalities of SPPs at the nano-scale. A variety of plasmonic waveguide structures which are applicable even in nano-photonic circuits, such as metallic strips and nanowires, V-grooves and gap structures have been proposed. Among them, the metal-insulator-metal (MIM) waveguides have attracted many interests for researchers because of the strong confinement of light and acceptable propagation length for SPPs. Some MIM devices based on SPPs, such as Y-shaped combiners, splitters, metamaterial and Mach-zehnder interferometers have been numerically and/or experimentally demonstrated as well.Utilizing the FDTD methods, in combination with perfectly matched layer (PML) boundary condition, to carry out the simulations of various filters based on MIM structures, such as MIM directional-coupling slit waveguide, slot cavity, tooth-grooves. Analyzing the principle of filter based MIM structure and two ways to separate the transmitted wave with single peak. Simulate the channel drop filter which is the basic cell of wavelength demultiplexing structure. Through adjusting the geometrical parameters of the structure, such as length and width of the slot cavity, coupled distance, to study the influences to the spectra and efficiency of transmission. Utilizing the influences of the geometrical parameters on the spectra of transmission, to carry out the simulations of wavelength demultiplexer based on the length and width of the slot cavity. By locating the last channel at the end of the bus waveguide and utilizing asymmetrical coupling simultaneously, enhanced transmission can be up to74%. Moreover, the transmission efficiency of the demultiplexing channels can be adjusted by shifting the last channel along the bus waveguide. |