INDEX barrier film

A novel polymer optical waveguide switch has been fabricated which uses total internal reflection from a thermally induced index barrier created by a silver stripe heater. In this case, polyurethane with An of -3.3 X 10 C" was used for the switching layer and PMMA was used for the substrate and buffer layers. A small part of the polyurethane film was left uncovered by the PMMA buffer to allow for injection of 632.8 nm He-Ne laser light into a single-mode waveguide by means of a prism-... 

Commercial barrier resins which are used as packaging films and blown bottles are produced by blending copolymers of acrylonitrile, ethyl acrylate, and butadiene with selected copolymers of acrylonitrile. These barrier resins have a Tg of about 125 C, a coefficient of linear expansion of 6.7 X 10 5 cm/cm C, a heat deflection temperature of 77 C, and an index of refraction of 1.511. These resins are resistant to nonoxidizing alkalis and acids and are decomposed by mineral acids. 

Critical issues associated with reflective or antirefiective coatings are the precise control of thickness and refractive index and, for multilayer films, development of a discrete, step-change in refractive index between layers. As reflected by the impressive production by Schott Glaswerke, the technology is sufficiently mature that these issues no longer constitute a barrier to the successful application of sol-gel technology. 

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