Study of Quasi-Phase-Matching Green Lasers based on Periodically Poled Lithium Niobate on Ridge Waveguides

This thesis focus on the fabrication of periodically poled lithium niobate on ridge waveguides (PPCLN on WG). It includes three parts: an introduction to the theory of waveguides and quasi phase matching (QPM), followed by the fabrication techniques, and the results of optical characterization. As for the fabrication part, we use the method of proton exchange and wet etching to make a ridge structure, which is followed by nickel diffusion to accomplish the realization of the optical waveguide structure. We then apply the pulsed electric field poling technique to realize PPCLN on the ridge waveguides. A PPCLN-WG with a periodicity of 6.7um, with ridge length of 6mm of height of 5.5um can thus be accomplished. As for the optical characterization part: a Nd:YVO4 1064nm laser with 18.8ns pulse width was used as the pump source. We report an observation of 20% conversion efficiency for second harmonic green generation at a pump power of 6mW, equivalent to peak pump intensity of 25.5MW/cm2. In comparison, bulk PPCLN pumped by 41mW 1064nm laser only gives a conversion efficiency of 1.2% due to a weak pump intensity of 7.6 MW/cm2 and lack of optical confinement in the mixing of nonlinear waves.