Surface modification of polymers by ionizing radiation: optical and mechanical effects

Abstract Ionizing radiation (light ions up to 200 keV and UV radiation with X < 280 nm) is used to structure thesurfaces of transparent polymers like poly-(methyl-methacrylate) and related materials. Areas with anindex increase up to 1 % sufficient for waveguiding are obtained. The method of waveguide fabrication in polymers by ionizing radiation is described in detail. The compaction of the irradiated areas accompanied by the index increase is used to make diffiactive structures. By a special embossingtechnique devices with directly coupled fibers are obtained. The chemical processes in the materialgenerated by the irradiation procedure are measured by spectroscopic methods, the optical propertiesof the components (refractive index profile, near field distribution, attenuation) are reported. 1. Introduction The rapid development of optical data transmission during the last decade has driven special techologiesto a high level. One of these special methods is the surface modification of polymers for the purpose ofmaking passive optical components as linking elements in silica fiber based optical networks. Routingand wavelength selection require low cost devices in mass production, a task which cannot performedneither by LiNbO3 nor anorganic materials. So polymer materials came into the field of interest and oneof the greatest challenges was the development of surface structuring of polymer substrates in order tomodify the optical properties as well as the surface morphology. Ionizing radiation, formerly more bychance than by intention found to be suitable for that purpose, has been established as a powerfiill toolfor fabrication of passive devices in polymers. Key components are the 1 :2 splitter for routing the lightand the Wavelength Division DeMultiplexer (WDDM) for spatial separating of different optical carrierwavelengths. Special aspects has been treated by Frank et 12452.