Focusing diffused waveguides

Focusing optical fibre and thin film guide can be made to have nearly the same group velocity for every mode if the optimum distribution of refractive index or thickness of the film is realized. A focusing optical fibre is manufactured from a multilayer glass rod by solid state diffusion. A thin film waveguide is prepared from nitrocellulose by controlling the airflow distribution. Undulation of light propagating in the film is observed, and it is confirmed that the focusing property is determined by the distribution of the film thickness. The field distributions of the TE modes have been analysed for an optical waveguide fabricated by solid state diffusion. Glass waveguide has been manufactured with the appropriate concentration of lead ions to give the maximum propagation constant. A low loss waveguide is fabricated by the diffusion of lead or thallium ion into glass followed by selective etching.