Transmission enhancement of light through subwavelength slit arrays in metallic films

Abstract

In this thesis, we present a study on the enhanced transmission of light and detailed properties of transmission spectra through sub-wavelength hole array in metallic films are investigated. The extraordinary transmission of light through subwavelength apertures were investigated by many researches and the main reason for this phenomenon has been known due to the excitation of surface plasmon polaritons(SPPs) on the surface of metal films which is caused by the coupling of incident light and SPP by structured surface of metallic films. We verified this transmission enhancement by an experimental measurements in microwave regime. The detailed transmission spectra show that the transmittance can either be suppressed or enhanced at specific wavelengths which depend on the geometry of the slit array, the material properties of the metal and dielectrics employed and the property of incident light such as the polarization and incident angle. In this study, sliver and perfect electric conductor(PEC) are chosen to construct the metallic films. The permittivity of silver is described as Drude model and the transmission spectra through slit arrays are obtained by the 2-dimensional finite-difference time-domain(FDTD) calculations at optical and infrared(IR) frequencies. In the case of the PEC, not only the FDTD calculations, but also an experiment in microwave regime with aluminum sample and analytical calculation of zeroth-order transmittance based on the scattering matrix which describes the coupling between the SPPs and the transmitted light in a metallic film are performed. Transmission peaks and dips are originated from the coupling between the incident light and SPPs which are caused by the slit array that acts like a grating coupler. The transmission spectra obtained both in the optical-IR regime for the silver film and in the microwave regime for the PEC film show similar dependence on the geometrical parameters. The experimentally measured results in micr...