Advanced fibre-based endoscopy for biophotonics applications

Despite the tremendous advances witnessed in light microscopy over the past two decades, non-invasive optical imaging is still limited to penetration depths smaller than 1 mm into tissue. Multiple scattering caused by the refractive index inhomogeneities of biological matter rapidly distort any optical wavefront prop-agating through, rendering tissues opaque. Such turbidity restricts imaging, as well as other biophotonics techniques, to the most superficial layers of tissue.<br/><br/>A perspective strategy to overcome the turbidity of living matter exploits holographic light control in multimode optical fibres. This allows devising min-imally invasive imaging probes with footprints far bellow those of conventional endoscopes, as well as enhanced spatial resolution up to the diffraction limit de-termined by the numerical aperture (NA) of the fibre.<br/><br/>In this Thesis, high-resolution focussing is demonstrated with unprecedented ability across novel specialty fibres offering very-high NAs, by devising a system and methodologies which allow counteracting the severe mode-dependent loss affecting such fibres. The high quality and NA of the generated foci is capable of 3D optical confinement of dielectric microparticles, thus enabling the deliv-ery of holographic optical tweezers introduced through a bare optical fibre with cross-section comparable to a single cell. The holographic methods developed allow the manipulation of complex 3D arrangements of particles, as well as their independent positioning with nanometre-scale precision in all three dimensions.<br/><br/>Separately, a multimode fibre based deep-brain fluorescence imaging is demonstrated in animal models in vivo, allowing the identification of neuronal structures at depths exceeding 2 mm and resolving fine details down to ≈1 µm resolution.

Name dc:type.qualificationname

Doctor of Philosophy

Level dc:type.qualificationlevel

Doctoral Thesis

Grantor dc:publisher.institution

University of Dundee

Year dc:date.issued

2018

Author dc:creator

• Oliveira Teixeira Leite, Ivo Jorge

Advisors dc:contributor.advisor

• Cuschieri, Alfred
• Cizmar, Tomas

Language dc:language

eng

Identifier

oai:discovery.dundee.ac.uk:studenttheses/c6ec5e01-199a-4caf-a154-a51633706ed2

OAI identifier oai:identifier

oai:discovery.dundee.ac.uk:studenttheses/c6ec5e01-199a-4caf-a154-a51633706ed2