Fabrication and Optical Properties of Periodic Long Range Order Nanoholes on Metallic Films

Long range order periodic structures of subwavelength apertures on optically thick metallic films have been investigated for their anomalous optical properties. Light transmission through an array of nanoholes is surprisingly higher than the prediction of the classical diffraction theorem and there is a consensus that this would be attributed to the excitation of the surface plasmon modes, a collective oscillation of the electrons on the surface of the metal due to interaction with the incident electromagnetic field. Long-range-order nanoholes array systems, contrarily to the more commonly studied short range structures, would provide several distinct advantages but the challenging fabrication process for these systems would be a major obstacle to overcome for their realization. In this thesis, it has been shown that for the long range order nanostructures of nanoholes array the spectrum of the transmitted light through the holes still showed the signature of the maxima and minima found in the transmitted spectrum for short range order systems. Experimental analysis of the spectra of these structures is however greatly simplified due to the increased total light transmission. One of the important applications of these structures is biosensing. The theoretical calculations showed that the higher flux of energy through the long range order periodic structures potentially increases the sensitivity of the biosensors based on the extraordinary optical transmission phenomenon. Two lithographic techniques based respectively on Electron Beam Lithography (EBL) and Nanospheres Lithography (NSL) for the fabrication of long range nanohole structures have been introduced. Spectra analysis of the structures by numerical calculations based on the 3 Dimensional Finite Difference Time Domain (3-D FDTD) reveals that the primitive model of momentum matching is not sufficiently accurate to predict the transmission spectra features and hence should not be relied on as a design tool. Instead, the transmitted spectra are interpreted as resulting from a combination of scattering and resonance modes, namely localized surface plasmons resonance, Wood anomalies and Surface Plasmon Polaritons modes.