B.S.T.J. Briefs: Sputtered Glass Waveguide for Integrated Optical Circuits

Sputtered Glass Waveguide for Integrated Optical Circuits By J. E. G O E L L and R. D. S T A N D L E Y (Manuscript received September 16, 1969) A series of papers which appeared in the September 1969 issue of the Bell System Technical Journal treated the theory of dielectric waveguides and stressed the potential use of such media for optical communication circuits. 1 - 4 Here we report on the realization of low-loss, thin glass films which can be used for circuit fabrication. Methods of preparing planar films and waveguides having rectangular cross section are described along with the techniques used in evaluating their optical characteristics. The films we used for waveguide fabrication have been prepared by RF Sputtering of suitable glasses. The sputtering system used was oildiffusion pumped and had five-inch diameter electrodes. Oxygen was used as the sputtering gas. The best films obtained to date were made by sputtering Corning 7059 glass. For convenience, in the early stages of this work, laboratory slides have been used as substrates. Necessary steps were taken to ensure that the substrates were clean. The index of refraction of the films was measured to be 1.62 by determining Brewster's Angle for the films as described by Abeles. 5 From the color of the film and by interferometer methods the film thickness was found to be about 0.3 ^m. The transmission loss of the films was measured by two methods. Both use prisms to launch a light beam into the film.0,7 In method 1 it is assumed that the scattering centers in the films are uniformly distributed.