GAS FILM LEVITATION : A UNIQUE CONTAINERLESS TECHNIQUE FOR THE PREPARATION OF FLUORIDE GLASS RODS

Containerless fabrication of fluoride glass rods using the gas film levitation technique has been developed to overcome some of the present limitations in the classical preparation by melt routes, namely (i) crucible interaction and associated contamination (platinum particles, chemical reactions) and (ii) mould interaction (mechanical stresses, surface defects). Further, the shaping ability of this technique allows the preparation of rod-like preforms for subsequent fibre drawing. Previous results have shown the ability of the technique to directly prepare test samples (discs) around 6 g in weight having Rayleigh light scattering losses near the intrinsic minimum values. In this paper, the preparation of fluoride glass rods (ZBLAN) by the gas film levitation technique is described and preliminary results on light scattering of glass rods thus prepared are presented. Present levitators are designed to process glass rods up to 50 g in weight in a batch process. An advanced levitation configuration, being developed to prepare long rods using a continuous replenishment process, is briefly presented.