VAPOR DIFFUSED OPTICAL WAVE-GUIDES IN STRONTIUM BARIUM NIOBATE (SBN-60)

Single mode planar and channel waveguides have been produced in Sr//0//. //6Ba//0//. //4Nb//2O//6 (tungsten bronze structure) by sulfur diffusion in a sealed ampule, followed by oxidation in an open tube. Losses in channel waveguides were approx. 15-20 dB/cm for TM polarization and approx. 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 LiNbO//3. Based on measurements with the S//3//5 radioisotope, the average atomic sulfur concentration was estimated to be about 4 multiplied by 10**1**7/cm**3 in the region extending from the surface to a depth of 2. 5 mu m, and a significant background concentration (approx. 5 multiplied by 10**1**6/cm**3) was present to depths in excess of 20 mu m.