Modified chalcogenide glasses for optical device applications

Hughes, MA 2007, Modified chalcogenide glasses for optical device applications , PhD thesis, University of Southampton.

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Abstract

This thesis focuses on two different, but complementary, aspects of the modification of gallium lanthanum sulphide (GLS) glasses. Firstly the addition of transition metal ions as dopants is examined and their potential for use as active optical materials is explored. It is also argued that the spectroscopic analysis of transition metal ions is a useful tool for evaluating the local environment of their host. Secondly femtosecond (fs) laser modification of GLS is investigated as a method for waveguide formation. Vanadium doped GLS displays three absorption bands at 580, 730 and 1155 nm identified by photoluminescence excitation measurements. Broad photoluminescence, with a full width half maximum of ~500 nm, is observed peaking at 1500 nm when exciting at 514, 808 and 1064 nm. The fluorescence lifetime and quantum efficiency at 300 K were measured to be 33.4 μs and 4% respectively. Analysis of the emission decay, at various vanadium concentrations, indicated a preferentially filled, high efficiency, oxide site that gives rise to characteristic long lifetimes and a low efficiency sulphide site that gives rise to characteristic short lifetimes. X-ray photoelectron spectroscopy measurements indicated the presence of vanadium in a broad range of oxidation states from V+ to V5+. Tanabe-Sugano analysis indicates that the optically active ion is V2+ in octahedral coordination and the crystal field strength (Dq/B) was 1.84. Titanium and nickel doped GLS display a single absorption band at 590 and 690 nm, and emission lifetimes of 97 and 70 μs respectively. Bismuth doped GLS displays two absorption bands at 665 and 850 nm and lifetime components of 7 and 47 μs. Based on comparisons to other work the optically active ions are proposed to be Ti3+, Ni+ and Bi+, all of these displayed emission peaking at ~900 nm. Through optical characterisation of fs laser written waveguides in GLS, a formation mechanism has been proposed. Tunnelling has been identified as the dominant nonlinear absorption mechanism in the formation of the waveguides. Single mode guidance at 633 nm has been demonstrated. The writing parameters for the minimum propagation loss of 1.47 dB/cm are 0.36 μJ pulse energy and 50 μm/s scanning speed. The observation of spectral broadening in these waveguides indicates that they may have applications for nonlinear optical devices. Fs laser written wave

Item Type: Thesis (PhD)
Schools: Schools > School of Computing, Science and Engineering
Funders: Engineering and Physical Sciences Research Council (EPSRC)
Depositing User: Dr Mark Hughes
Date Deposited: 05 Jun 2017 12:10
Last Modified: 05 Jun 2017 12:10
URI: http://usir.salford.ac.uk/id/eprint/37020

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