Fabrication and characterization of high-damage resistance Zn-diffused MgO: PPLN ridge waveguides

Abstract

This study investigates the fabrication process of Zn-diffused ridge waveguides in periodically poled magnesium-doped lithium niobate (PPMgO: LN). A controlled variable method is used to study the effects of diffusion temperature, diffusion time, ZnO film thickness, and barrier layer thickness on the surface domain depolarization and waveguide quality of PPMgO: LN. A special barrier layer is proposed that can automatically lift off from the sample surface, which increases the depth of Zn doping and reduces the surface loss of the waveguide. By optimizing the process parameters, we fabricate Zn-diffused PPMgO: LN ridge waveguides with a length of 22.80 mm and a period of 18.0 µm. The above waveguides can make a second harmonic generation (SHG) at 775 nm with an output power of 90.20 mW by a pump power of 741 mW at 1 550 nm. The corresponding conversion efficiency is 3.160%/W·cm², and the waveguide loss is approximately 0.81 dB/cm. These results demonstrate that high-efficiency devices can be obtained through the fabrication process described in this paper.

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