Abstract

Recently we reported a channel dropping filter¹ using the coupling from a surface K⁺–Na⁺ guide across a low index interlayer to a multimoded overlay film. An improvement on the design was sought by the introduction of a buried waveguide. Burying of K⁺–Na⁺ waveguides was first reported using an electric field assisted process² where both planar and narrow channel guides (width < 10/1m) were fabricated. However, only planar^3,4 and wide channel guides (30µm)5 have thus far been demonstrated by thermal backdiffusion. Here we report a new diffusion recipe allowing the fabrication of narrow, single mode channel guides for wavelength filters by a purely thermal process.

© 1993 Optical Society of America