Tuneable Sum-Frequency Generation and Spectral Broadening Based on Proton-Exchanged Thin-Film Lithium Niobate Ridge Waveguide

How to simultaneously generate sum-frequency (SF) generation (SFG) and achieve spectral broadening has always been a research focus in spectral measurement and optical imaging. In this study, we have achieved SFG and spectral broadening for the first time in a proton-exchanged thin-film lithium niobate ridge waveguide. By adjusting the wavelength of the continuous laser, we could dynamically tune the center wavelength of the SF light and the width of the spectral broadening. Wherein the highest normalized conversion efficiency of harmonic light was 1048.1% W1- cm(-2), the normalized conversion efficiency of SF light was 345.9% W1- cm(-2), while we achieved a tuning width of up to 80 nm for the SF light. Additionally, tuneable spectral broadening can be effectively achieved by designing an effective waveguide dispersion and utilizing self-phase and cross-phase modulation between photons, with a broadening range of up to 84-107 nm, and bidirectional modulation can be achieved. The successful implementation of this work opens up new possibilities for on-chip spectral detection, on-chip imaging, and a tuneable broadband light source, providing novel insights into the field.