Quasi-Phase-Matched Difference Frequency Generation Devices with Annealed/Proton-Exchanged LiNbO3 Waveguides Buried by Reverse Proton Exchange

Annealed/proton-exchanged LiNbO3 waveguides buried by reverse proton exchange were studied and applied to quasi-phase-matched difference frequency generation (DFG) devices to improve their efficiency. A device of 3.1 cm length was fabricated and characterized. In preliminary second harmonic generation experiments, four-fold improvement in the normalized efficiency was demonstrated. In DFG wavelength conversion experiments, conversion efficiency of -9 dB for pump power of 12 mW was achieved. The corresponding normalized DFG efficiency was 1000%/W, which is, to the best of the authors' knowledge, the highest value ever reported.