Ga-La-S glass with GaSe additions to produce compatible core/clad pairs for IR optical fibre fabrication via extrusion

Gallium-Lanthanum-Sulphide (GLS) glasses have been investigated as candidate materials for fabrication of IR transmitting optical fibres. However, due to the thermo-viscous behaviour and the low stability of the glasses (defined by T-crystauisaion-T-draw) producing strong, optical fibres has proven, difficult. The most successful compositions have contained a high percentage of added La2O3 (up to 50 wt%) to increase stability and improve the fibre drawing ability. The oxide additions also allow the tailoring of the RI the produce compatible core/clad pairs, however oxide additions have a detrimental effect on the IR transparency of the material. Another method of lowering the RI of GLS is to substitute La2S3 with Na2S to produce a cladding glass.

A method of extrusion has been proposed that can be used to produce core/clad optical fibre performs. In this work a new method of altering the RI of the GLS glasses is investigated. As an alternative to lowering the RI to produce a cladding glass, the RI was increased to produce a core glass. This was done by small additions of GaSe to the standard GLS composition, producing GLSSe glasses, avoiding the need for unfavourable oxide additions. It is suggested that this will produce high index core glasses with favourable thermal properties for the extrusion and fibre drawing process. Extrusion, preform fabrication and fibre drawing will be reported.