Stable Proton Exchanged Waveguides in Lithium Tantalate

$\alpha$, $\beta_{1}$, and $\kappa_{2}$ phases are investigated for planar waveguide fabrication by proton exchange in congruent lithium tantalate. The effective indices of planar waveguide eigenmodes were monitored over time, revealing that the exchange process induces aging instabilities in all phases except $\alpha$ .