Watt-level 775 nm SHG with 70% conversion efficiency and 97% pump depletion in annealed/reverse proton exchanged diced PPLN ridge waveguides

We report on fabrication of ridge waveguides formed in congruent periodically poled lithium niobate substrates using annealed and reverse proton exchange followed by diamond blade dicing. 1 W of second-harmonic generation at 775 nm has been obtained in a single-pass in 50 mm long ridge waveguides with internal conversion efficiency of 70%. At this power level, 97% pump depletion has been reached. Although elevated temperature operation and ridge geometry help to mitigate photorefractive damage (PRD) effects, nevertheless, at even higher second harmonic outputs significant power drop with blue shift and distortion of the SHG tuning curve have been observed indicating an onset of PRD.