Year

2017

Degree Name

Doctor of Philosophy

Department

School of Physics

Abstract

Terahertz methods have developed strongly in recent years resulting in an emergence of applications spanning many research fields. This is owing to desirable properties of the terahertz wave; large penetration depths in dielectric materials with non-ionisation, coupled with the origin of many physical phenomena, like vibrational modes, occurring at terahertz frequencies. This thesis explores these advantages in two contemporary research areas; 3D printing and art conservation science.

3D printing is shown to be a desirable modality to couple with terahertz techniques with printable dielectric materials allowing for rapid, customisable terahertz components, even with the cheapest and simplest form, fused filament fabrication. Specifically, commercial filament materials are characterised and evaluated in the terahertz regime in conjunction to producing functional components, namely diffractive optics and a hyperuniform waveguide.

Terahertz applications in art conservation science are investigated through critical analysis of a series of synthetic and natural pigments. Quinacridone and phthalocyanine, the most important synthetic pigments in red-violet and blue-green shades respectively are shown to have `fingerprint' spectra, with associated temperature dependence. Terahertz photons distinguish polymorphs of these pigments, not achievable with competing modalities using x-rays. Earth-based iron oxide pigments found in many indigenous and culturally significant artefacts also show characteristic, sometimes temperature dependent, absorptions for terahertz frequencies. Strong distinction is shown for natural and synthetic counterparts of the same pigment class with subtle variations in similar pigments from varying geographical origins. Terahertz spectroscopy confirms utility in this research field in identifying optically similar materials, fraud detection in reproductions, dating of artworks and sourcing the geographical origin of culturally significant items.

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