Single mode planar and channel waveguides have been produced in Sr 0.6Ba0.4Nb2O6 (tungsten bronze structure) by sulfur diffusion in a sealed ampule, followed by oxidation in an open tube. Losses in channel waveguides were 15-20 dB/cm for TM polarization and 27-32 dB/cm for the TE polarization in z-cut substrates. Electro-optic modulation was observed after poling of the substrate. The experimentally determined value of the effective electro-optic coefficient was slightly greater than reported earlier for bulk samples of SBN:60, and about 15 times greater than for LiNbO3. Based on measurements with the S 35 radioisotope, the average atomic sulfur concentration was estimated to be about 41017/cm3 in the region extending from the surface to a depth of 2.5 m, and a significant background concentration (51016/cm 3) was present to depths in excess of 20 m.
