A study was made of the behavior of the extraordinary refractive index of a set of annealed z-cut proton-exchanged substrates by means of optical prism-coupling measurements and numerical simulations. The values of the index, as a function of depth, were determined and were fitted by a single Gaussian diffusion expression. At 400C, the effective index diffusivity of 4.6 x 10-12cm2/s was almost identical to the diffusivity of substitutional H in these samples. A linear relationship was found between increases in the extraordinary refractive index and the substitutional H concentration. At a wavelength of 0.6238, the proportionality coefficient in this relationship was 1.5 x 10-23(H/cm3)-1.

J.M.Zavada, H.C.Casey, C.H.Chen, A.Loni: Applied Physics Letters, 1993, 62[22], 2769-71