Waveguides, planar fluoride glass

Typical of sodium-containing glasses such as ZBLAN or BIG-Na, another way to increase the refractive index is to substitute Li+ for Na+ ions, despite the lower polarizability of lithium ions because of their small size. Actually, Li+ ions are so small that they induce a local collapse of the glassy network resulting in an increase of the densification and of the refractive index [10,24,25]. This property is utilized for the elaboration of fluoride glass planar waveguides by ionic exchange, as described in Sec. 5.3. 

Table 11.3 Comparison of fabrication methods and characteristics (refractive index change, thickness and propagation loss) of fluoride glass planar waveguides...

C. Charron, E. Fogret, G. Fonteneau, R. Rimet, J. Lucas, Fluoride glass planar optical waveguides, J. Non-Cryst. Solids, 184, 222-224 (1995). 

Planar and channel waveguides can be obtained by ion-exchange technique with fluoride glasses. The experiment is carried out with Er +-doped ZBLA fluoride glass samples, treated by HCl gas at a temperature below the glass transition temperature Tg (Tg = 307 °C for ZBLA). The chemical reaction at the glass surface is ... 

Table 11.1 Chemical composition, thermal and physical properties of fluoride glasses used to achieve planar waveguides, a is the vibration frequency that accounts for the multiphonon absorption...

A.J. Bruce, G. Zydzik and M. Chui-Sabourin, Heavy metal fluoride glass films and planar waveguide structures. Mat. Sc. Forum, 25, 671-675 (1990). 

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