Microspectroscopy of localised plasmons

Abstract

Working with nanoscale optics requires methods and equipment designed for the purpose. This thesis describes the development of techniques and a system for performing highly localised spectroscopy. The system consists of a nanonics mul- tiview 2000 scanning near-�eld optical microscope, a grating spectrometer and a photonic crystal �bre supercontinuum light source. Discussion of the microscope includes its modes of operation and development of software to collect and anal- yse data. In order to demonstrate the setup, an example of localised spectroscopy is presented in the form of an investigation of hollow core photonic crystal �bre. Taking spectra of the components of the cladding of these �bre makes it possible to investigate the origins of bandgap guidance. A core focus of nanoscale optics is the interaction of light with metal structures. This �eld is called plasmonics. Fabrication of structures is presented and re- quires special facilities and processes. These processes are both time consuming and expensive, both factors that emphasise the a need for prior modelling. For- ward di�erence time domain modelling of a proposed structure comprising of a concentrically arranged ring and disk is explored using home written code and a commercial package called CST Microwave Studio. The investigation of this concentric design through modelling shows a very highly localised �eld enhance- ment which can be engineered to have a narrow spectral resonance in the near infra-red. The interaction of the two components which govern this resonance is explained using a theory called plasmon hybridization. Once the optical behaviour of small metal objects is understood they can be used in other ways. An example of this is shown in Porous Silicon. As a material it provides an excellent template for formation of metal nano-particles. Embedded in a high surface area network of silicon these particles can be used as very effcient catalysts.

Date of Award	1 Jan 2009
Original language	English
Awarding Institution	University of Bath
Supervisor	Stefan Maier (Supervisor)