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Compositional effects on the thermo-optic coefficients of potassium aluminophosphate glasses

Compositional effects on the thermo-optic coefficients of potassium aluminophosphate glasses
Compositional effects on the thermo-optic coefficients of potassium aluminophosphate glasses
The central wavelength of lightwave devices such as gratings is sensitive to temperature, due to the temperature dependence of the devices' optical path lengths. One way to solve this problem is to use an athermal device. Phosphate glasses are ideal hosts for such devices as they exhibit negative thermo-optic coefficient (dn/dT), which counters the effect of expansion. For this study, fourteen different compositions of potassium aluminophosphate glasses, of the K2O-Al2O3-P2O5 system, were prepared with O/P ranging from 2.8 to 3.1. Refractive indices, glass transition temperature (Tg), coefficient of thermal expansion (CTE) and thermo-optic coefficient (dn/dT) measured for the glasses are what is expected with the addition of aluminium : an increase in Tg and a reduction in CTE. Tg changes in the range of 272°C to 621°C while CTE decreases from 21x10-6/°C to 7x10-6/°C as the aluminium content increases. We are able to achieve dn/dT value as negative as -16x10-6/°C. In addition, the glasses are thermally stable, judging by the large difference between Tg and the temperature of onset of crystallisation. Athermal glasses have been achieved at low aluminium content with high CTE, which in turn leads to negative dn/dT. These results are consistent with the polarisability effect in the glasses as low aluminium content lowers polarisability, which gives rise to negative dn/dT. The CTE of glasses must be more than 10x10-6/°C to achieve negative dn/dT. Any deficit or excess P2O5 does not seem to affect the CTE and dn/dT.
Lee, E.T.Y.
c687873a-9418-4b42-a083-487f993b4ed4
Taylor, E.M.
0df42215-6e9b-4f54-ac49-f8f76261056d
Lee, E.T.Y.
c687873a-9418-4b42-a083-487f993b4ed4
Taylor, E.M.
0df42215-6e9b-4f54-ac49-f8f76261056d

Lee, E.T.Y. and Taylor, E.M. (2003) Compositional effects on the thermo-optic coefficients of potassium aluminophosphate glasses. Glass and Optical Materials Division Fall Meeting, Corning, USA. 11 - 14 Oct 2003.

Record type: Conference or Workshop Item (Paper)

Abstract

The central wavelength of lightwave devices such as gratings is sensitive to temperature, due to the temperature dependence of the devices' optical path lengths. One way to solve this problem is to use an athermal device. Phosphate glasses are ideal hosts for such devices as they exhibit negative thermo-optic coefficient (dn/dT), which counters the effect of expansion. For this study, fourteen different compositions of potassium aluminophosphate glasses, of the K2O-Al2O3-P2O5 system, were prepared with O/P ranging from 2.8 to 3.1. Refractive indices, glass transition temperature (Tg), coefficient of thermal expansion (CTE) and thermo-optic coefficient (dn/dT) measured for the glasses are what is expected with the addition of aluminium : an increase in Tg and a reduction in CTE. Tg changes in the range of 272°C to 621°C while CTE decreases from 21x10-6/°C to 7x10-6/°C as the aluminium content increases. We are able to achieve dn/dT value as negative as -16x10-6/°C. In addition, the glasses are thermally stable, judging by the large difference between Tg and the temperature of onset of crystallisation. Athermal glasses have been achieved at low aluminium content with high CTE, which in turn leads to negative dn/dT. These results are consistent with the polarisability effect in the glasses as low aluminium content lowers polarisability, which gives rise to negative dn/dT. The CTE of glasses must be more than 10x10-6/°C to achieve negative dn/dT. Any deficit or excess P2O5 does not seem to affect the CTE and dn/dT.

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e-pub ahead of print date: 2003
Venue - Dates: Glass and Optical Materials Division Fall Meeting, Corning, USA, 2003-10-11 - 2003-10-14

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Local EPrints ID: 41576
URI: http://eprints.soton.ac.uk/id/eprint/41576
PURE UUID: 97211546-3086-46fe-80a1-cd28510a2bce

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Date deposited: 03 Oct 2006
Last modified: 11 Dec 2021 15:56

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Contributors

Author: E.T.Y. Lee
Author: E.M. Taylor

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