Optical waveguiding in doped poly(methyl methacrylate)

Channel-optical-waveguide fabrication based on electron-beam irradiation of polyimides

A new-channel-waveguide-fabrication process for use with polyimide is described. The new technique uses an electron-beam-induced effect to alter the refractive index of the polyimides directly. Channel waveguides with an 8-µm-wide, 8-µm-deep core have been fabricated on a polyimide film by the use of electron-beam irradiation. Only one kind of polyimide (6FDA/TFDB) was used in this waveguide. The difference in refractive index between the core and the cladding was approximately 0.30% for both TEand TM-polarized incident light when the dose was 1500 µC/cm(2), which was sufficient to produce waveguides. The optical properties of the waveguide are also demonstrated.

Fabrication and characterization of dye doped polyester-polyurethane optical waveguides

A systematic study of the fabrication and characterization of planar optical waveguides based on polyester-polyurethane coatings was done. Mode effective refractive index measurements were performed on a large number of these waveguides fabricated on glass substrates prepared in different conditions. The results indicate that the effect of the dye is to increase the refractive index of the waveguides. The losses in the guides, however, initially decreased from 0.9 to approximately 0.5 dB/cm when the dye concentration was approximately 0.1% but increased drastically (>30 dB/cm) for guides with greater dye concentrations.

Evaluating polyimides as lightguide materials

Lightguides were fabricated from three commercial polyimides of which one contains one and the others contain two hexafluoroisopropylidene (6F) groups. The latter are isomers using either the para or the meta isomer of the same diamine. As the number of 6F groups increases the optical losses of the corresponding lightguides decreases. In thick lightguides of the two 6F groups containing polyimides, loss values below 0.1 dB/cm can be realized using optimized conditions. Two mechanisms-ordering with or without charge transfer complex formation and voids or pinholes-are seen to be responsible for optical losses. The second type of losses can be reduced by cure optimization. Where ordering is possible annealing leads to increased optical losses. Geometrical restraint of the ordering, however, leads to loss reduction in otherwise identical conditions. Losses observed in the bulk are always higher than in the top and bottom layers of the polyimide films.