High quality buried waveguides in stoichiometric LiTaO3 for nonlinear frequency conversion

High-quality buried optical-waveguides were fabricated by reverse-proton-exchange in periodically-poled stoichiometric lithium tantalate. Experimental results show excellent fiber-mode matching, losses below 0.3 dB/cm and almost non-critical conditions for a quasi-phase-matched second-harmonic generation process from telecom wavelengths. The interaction length of 2.5 cm is the highest so far reported for lithium tantalate waveguides.