Intensity‐dependent index of refraction in multilayers of polydiacetylene

We have grown multilayer samples of a polydiacetylene upon a metallized grating forming a planar waveguide structure. By measuring the change with optical intensity in the coupling angle between an input laser beam and a planar waveguide mode in the structure we estimate the intensity‐dependent index of refraction, n2≂10−6 (MW/cm2)−1 (λ>7500 A), for the polydiacetylene. Also, a large resonant enhancement of the optical nonlinearity was observed.