Characterisation of passive polymer optical waveguides

The characterisation of monomode passive polymer optical devices fabricated according to the POPCORN technology by methods originated from electron, ion and optical spectroscopy is summarized. Impacts of observed waveguide perturbations on the optical characteristics of the waveguide are evaluated. In the POPCORN approach optical components for telecommunication applications are fabricated by photo-curing of liquid halogenated (meth)acrylates which have been applied on moulded thermoplastic substrates. For tuning of waveguide material refractive indices with respect to the substrate refractive index frequently comonomer mixtures are used. The polymerisation characteristics, especially the polymerisation kinetics of individual monomers, determine the formation of copolymers. Therefore the unsaturation as function of UV-illumination time in the formation of halogenated homo- and copolymers has been examined. From different suitable copolymer systems, after characterisation of their glass transition temperatures, their curing behaviour and their refractive indices as function of the monomer ratios, monomode waveguides applying PMMA substrates have been fabricated. To examine the material composition also in the 6 x 6 mu m(2) waveguides they have been visualised by transmission electron microscopy. With this method e.g. segregation phenomena could be observed in the waveguiding copolymer with features in the 100 nm range. Secondary ion mass spectrometry has been used for waveguide cross section characterisation as well. The optical losses in monomode waveguides caused by segregation and other material induced defects like micro bubbles formed as a result of shrinkage have been quantisized by return loss measurements. Defects causing scattering could be observed by convocal laser scanning microscopy and by conventional light microscopy.