Stoichiometry-Control and the Performance of Electrooptic Waveguides for Integrated Optics

The laser power-handling performance of diffused lithium niobate planar waveguides, as limited by their development of laser-induced optical damage, is characterized in terms of the pertinent chemical process variables involved in their production. Lithium niobate waveguides are formed by the out-diffusion of lithium oxide under oxidizing conditions, by the in-diffusion of titanium, and by out-diffusion under nonoxidizing conditions. These three waveguide types, however, exhibit radically different laser power-handling capabilities. Out-diffused waveguides prepared under oxidizing conditions, as compared with equivalently prepared titanium in-diffused guides, are able to handle more than twenty times the laser power, at the same level of performance. An out-diffused waveguide propagates 1-5 mW at 632.8 nm with less than 2-6 percent steady-state output power loss. Out-diffused waveguides prepared under nonoxidizing conditions exhibit rapid power loss followed by equally rapid and full steady-state recovery. Waveguide chemistry, on the other hand, does not alter the manner in which the laser power is dispersed in the plane of the waveguide. Laser power is always scattered within the waveguide plane, to the negative c-axis side of the centrally propagating laser beam.