Sum-frequency generation in a high-quality thin film lithium niobate microdisk via cyclic quasi-phase matching

Whispering-gallery-mode (WGM) microresonators can dramatically boost the interaction between light and matter, making them an ideal platform for studying nonlinear optics. Efficient wavelength conversion by nonlinear parametric processes is key to integrated optics in many applications, where WGM microresonators play an important role. Here, we demonstrate efficient second-harmonic generation (SHG) and sum-frequency generation (SFG) in an x-cut thin film lithium niobate microdisk with a high intrinsic quality factor over 10 6 . The normalized conversion efficiency of cyclic quasi-phase-matched (CQPM) SHG and SFG is measured to be 1.53%/mW and 2.52×10 −4 /mW, respectively. Our work expands nonlinear optics applications of CQPM WGM microresonators as efficient wavelength convertors for light upconversion.