This Small Business Innovation Research Phase I project will demonstrate the feasibility of fabricating waveguides in stoichiometric lithium tantalite (SLT) for highly efficient, quasi-phase matched (QPM) frequency conversion of continuous wave and high peak-power, quasi-continuous laser sources used in lidar-based remote sensing and ranging applications. The key innovation in this effort is the use of large diameter, optical quality, z-cut SLT, which has only recently become commercially available, as the waveguide substrate material. Relative to the standard congruently grown lithium tantalate wafers, stoichiometric lithium tantalate wafers have significantly higher optical damage thresholds, stronger nonlinear and electro-optic response, an expanded transparency window and significantly reduced poling field. Furthermore, because the stoichiometric materials are not lithium deficient, the fabricated waveguides are expected to be optically stable. During the Phase I effort the feasibility of fabricating waveguides in z-cut SLT wafers using annealed proton exchange will be determined, and the impact that variations in processing conditions have on the optical properties will be measured. In the Phase II effort, the waveguide fabrication and poling technology will be refined and grating structures suitable for specific NASA applications requiring wavelength conversion.