The University of Southampton
University of Southampton Institutional Repository

Development and characterisation of phosphate glasses for athermalisation

Development and characterisation of phosphate glasses for athermalisation
Development and characterisation of phosphate glasses for athermalisation
Lightwave devices such as gratings have a drawback where the central wavelength of the devices is sensitive to changes in temperature, which compromises their performance. This problem is particularly acute in systems that employ Wavelength Division Multiplexing (WDM), where the stability of wavelength with regards to temperature is essential. An athermal waveguide, which is inherently insensitive to temperature, is an ideal choice to solve this problem instead of using a passive temperature control unit, which could limit the optimum performance of a WDM system.

Generally, athermal glasses must exhibit negative refractive index change with temperature (dn/dT) to counter the effect of thermal expansion. Phosphate glasses are ideal candidates for athermalisation as they exhibit negative dn/dT. An interferometer set-up has been constructed to specifically measure dn/dT of the glasses.

Three different phosphate glass families were prepared and characterised in terms of their optical and thermal properties. The properties of the potassium aluminophosphate glasses were strongly influenced by the strengthening effect of Al3+, the trend observed for the binary phosphate glasses depended on the availability of terminal oxygens to coordinate the cations while the change in the properties of borophosphate glasses depended on the effect and coordination number of B3+. Glasses with negative dn/dT have been achieved from the various compositions of glasses studied. The results showed that there was a minimum thermal expansion coefficient (α) for each glass system, beyond which α would overcome the effect of polarisability change with temperature so that the glasses exhibited negative dn/dT. Semi-empirical equations linking dn/dT and α have been defined, enabling the estimation of dn/dT of any glass within the same system. This research work represents the first comprehensive measurement of dn/dT of phosphate glasses.

Both fibre and planar waveguides were fabricated. Extrusion was used to prepare the preform for fibre drawing. The extrusion process used a two-die assembly to extrude dissimilar glasses, and is the first demonstration of its kind. The spin-coating process was used to deposit layers of glass on glass substrates to produce planar structures. The success of the extrusion and spin-coating work showed that these processes could be used for combinations of glasses with dissimilar thermal properties. Femtosecond writing was investigated on the phosphate glasses and channel waveguides have been successfully defined.
Lee, E.T.Y.
c687873a-9418-4b42-a083-487f993b4ed4
Lee, E.T.Y.
c687873a-9418-4b42-a083-487f993b4ed4

Lee, E.T.Y. (2004) Development and characterisation of phosphate glasses for athermalisation. University of Southampton, Faculty of Engineering, Science and Mathematics, Optoelectronics Research Centre, Doctoral Thesis, 236pp.

Record type: Thesis (Doctoral)

Abstract

Lightwave devices such as gratings have a drawback where the central wavelength of the devices is sensitive to changes in temperature, which compromises their performance. This problem is particularly acute in systems that employ Wavelength Division Multiplexing (WDM), where the stability of wavelength with regards to temperature is essential. An athermal waveguide, which is inherently insensitive to temperature, is an ideal choice to solve this problem instead of using a passive temperature control unit, which could limit the optimum performance of a WDM system.

Generally, athermal glasses must exhibit negative refractive index change with temperature (dn/dT) to counter the effect of thermal expansion. Phosphate glasses are ideal candidates for athermalisation as they exhibit negative dn/dT. An interferometer set-up has been constructed to specifically measure dn/dT of the glasses.

Three different phosphate glass families were prepared and characterised in terms of their optical and thermal properties. The properties of the potassium aluminophosphate glasses were strongly influenced by the strengthening effect of Al3+, the trend observed for the binary phosphate glasses depended on the availability of terminal oxygens to coordinate the cations while the change in the properties of borophosphate glasses depended on the effect and coordination number of B3+. Glasses with negative dn/dT have been achieved from the various compositions of glasses studied. The results showed that there was a minimum thermal expansion coefficient (α) for each glass system, beyond which α would overcome the effect of polarisability change with temperature so that the glasses exhibited negative dn/dT. Semi-empirical equations linking dn/dT and α have been defined, enabling the estimation of dn/dT of any glass within the same system. This research work represents the first comprehensive measurement of dn/dT of phosphate glasses.

Both fibre and planar waveguides were fabricated. Extrusion was used to prepare the preform for fibre drawing. The extrusion process used a two-die assembly to extrude dissimilar glasses, and is the first demonstration of its kind. The spin-coating process was used to deposit layers of glass on glass substrates to produce planar structures. The success of the extrusion and spin-coating work showed that these processes could be used for combinations of glasses with dissimilar thermal properties. Femtosecond writing was investigated on the phosphate glasses and channel waveguides have been successfully defined.

Text
Lee_2004_thesis_2951 - Author's Original
Restricted to Repository staff only
Available under License University of Southampton Thesis Licence.

More information

Published date: 2004
Organisations: University of Southampton, Optoelectronics Research Centre

Identifiers

Local EPrints ID: 15466
URI: http://eprints.soton.ac.uk/id/eprint/15466
PURE UUID: 1c839277-eccf-467b-8bdf-feaf0b53fbe4

Catalogue record

Date deposited: 20 Apr 2005
Last modified: 12 Jul 2021 16:33

Export record

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×