Mesoporous Silicon Photonic Device Applications

Abstract

The research into artificial materials, including meta-materials, have made huge advances, and yielded new materials with unique set of features that cannot be found in nature. Such materials have opened the door for new applications and improving the already existing ones. In this research I have used material structural design to achieve the desired optical properties for each of the applications mentioned in this thesis. All samples fabricated and tested in this research were 1-dimensional porous silicon (PSi) structures. Porous silicon was chosen because it can be considered as an accessible, easy to fabricate photonic meta-material where pores shape, size and density are analogous to the inclusions and additions in meta-materials, while structuring of the layers and their thicknesses act as a photonic crystal. The aim of this research is to exploit structuring in one-dimensional photonic crystals in order to control the spatial, temporal and phase distribution of reflected waves. I focused on three main fronts. The first one is omnidirectional reflection. The existence of Brewster angle has been a considerable obstacle when it comes to omnidirectional reflectors. It restricts the extension of omnidirectional bands to high refractive index incident media. I have shown that it is possible to achieve omnidirectional reflection in both rarefied and refracting incident media utilising periodic structures consisting of three or more distinct layers with differing refractive indices. In these ternary periodic structures the Brewster condition is not satisfied simultaneously at all interface and so, strong reflection bands are achievable at any angle of incidence and polarisation state. I have shown the concept theoretically and experimentally. The second application is to use double chirping technique to eliminate unwanted oscillations in dielectric reflectors. The theory was tested thoroughly and lab measurements confirmed my simulations. The third area is utilising Fano resonance in 1-D PSi structures for biosensing, were I demonstrated theoretically the use Fano resonance in 1-D PSi structure to detect the presence of target analyte by monitoring the changes in the Fano lineshape upon the target analyte infiltration into the pores which changes the refractive index of the top layer.