A NEW METHOD FOR PRODUCING GRADED-INDEX PMMA WAVE-GUIDES

We report a new method for producing graded index polymethyl methacryl ate (PMMA) waveguides using optical densification by angled x-ray expo sure. The resulting larger refractive index near the surface of the wa veguide serves to better isolate the guided light from potentially abs orbing or scattering substrates than in waveguides of constant refract ive index, We calculate that a 65 degrees angle exposure in 6-mu m-thi ck planar PMMA waveguide shifts the peak of the fundamental mode profi le similar to 0.5 mu m away from the substrate, Consistent with this r esult, we measure a reduction In the propagation loss of PMMA planar w aveguides on a Ni substrate from 1.5 dB/cm to 0.5 dB/cm after angle x- ray exposure.