Compositional Characterisation of Optical InGaSb-core Microfibres
Abstract
This thesis constitutes the first step on the way to understanding and applyingthe ternary InGaSb-semiconductor alloy in the field of nonlinear fibre optics. Thissemiconductor material is also interesting for applications in the infrared domain.Using InGaSb in the core has the potential to greatly influence especially the THzpower delivery, since the bandgap and optical properties can be tuned by changingthe composition.In this work the individual binary compounds, GaSb and InSb, and ternarycompounds In0.3Ga0.7Sb and In0.5Ga0.5Sb have been hand-drawn into fibres. Todetermine the best candidates, different glasses and coatings were tested, thosewere AR-glass, AR-glass modified with NaKCl, DURAN and DURAN modified withNa2PO4. Investigation using SEM, EDS and Raman spectroscopy indicated that thecore materials exhibit crystal structures with the expected phases, but also oxidationand diffusion of some of the glass and coating elements in the core, most prominentin the In-based fibres. DURAN seemed to be best suited for the GaSb-compound.This glass coated with Na2PO4 seemed to work best for the InSb-compound.The use of CO2-laser irradiation to heat the glass cladding and thereby recrystallisethe core showed promising results upon formation of single crystal GaSb.Similar treatment of the In0.5Ga0.5Sb-core fibre looked, by XCT micrographs, tohave homogenised the compound to some degree. It is suspected that a too smalltemperature and/or a too high translation velocity of the laser during process leadto constitutional undercooling with some local non-uniformities as result. However,critical assessment