Abstract: ew the effects of variations in effective mode indices and dispersion on the design and characterization of polymeric waveguides for frequency conversion and photoinduced diffraction in integrated optics devices. Device design in each case depends critically on the effective index of refraction of light propagating in the waveguide which may be a function of the intensity and device history. In detail we report on the conditions for anomalous dispersion phase matching in nonlinear waveguides and on techniques for measuring photoinduced diffraction in prism coupled waveguides. With respect to the latter, diffraction effects due to photochromic gratings in slab waveguides of disperse red 1 in polymethylmethacrylate were studied. Optical damage in the form of diffractive mode conversion was observed when light whose wavelength was slightly longer than the absorption edge of disperse red 1 was coupled in. We also investigated the effect of mode coupling changes on the determination of diffraction efficiency and sensitivity in waveguide experiments using two crossed guided beams. Diffraction efficiencies predicted by measurements of the modulation depth in the guide are found to overstate the actual diffraction efficiencies which could be observed in this geometry. Techniques for overcoming this limitation and for improving estimates of the energy density and interaction length in the guide are noted. !24
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