Highly Efficient $+$5-dB Parametric Gain Conversion Using Direct-Bonded PPZnLN Ridge Waveguide

We fabricated a 50-mm-long ZnO-doped quasi-phase-matched LiNbO ridge waveguide by employing the direct bonding and dry etching techniques. We obtained a second-harmonic generation conversion efficiency of 2400%/W and a second-harmonic output power of 148 mW with a pump power of 160 mW. We demonstrated 1.55-m-band wavelength conversion based on a cascade scheme. A parametric conversion gain of 5 dB was successfully achieved.