The study of waveguides made by diffusion of Br into AgCl substrates and the transmission of mid-IR radiation through these waveguides

Silver halide crystals of the form AgClxBr1-x can be grown from the melt in all ratios of Cl:Br and they are highly transparent in the middle infrared. The index of refraction of such mixed crystals increases monotonically with x, from that of AgCl (x = 1, n = 1.98) to that of AgBr (x = 0, n = 2.16). These properties suggested that they could be used to form graded index waveguides for the mid-IR. Cylindrical ingots of crystals of composition AgCl0.9Br0.1 and AgCl0.1Br0.9 were grown; discs from each were cut and polished and placed in optical contact at 410 degreesC. Diffusion of Br ions from the Br-rich side to the Cl-rich side produced a graded index waveguides whose thickness was determined by the diffusion time. The diffusion depth was obtained by scanning electron microscopy and by optical methods. These studies provide information about the diffusion coefficients of ions in silver halide crystals and the optical properties of the diffused layers. These silver halide waveguides will be useful as integrated optical elements in the mid-IR. (C) 2001 Published by Elsevier Science B.V.