Annealed Proton-Exchanged LiNb03 Ridge Waveguides -- Simulation, Fabrication and Characterization

Abstract

<p>Although semiconductor optical waveguides are quite mature in industry productions, fabrication of high quality lithium niobate (LiNb0₃) waveguides has always been a challenging topic over the past decades. Intense studies have been done, and various kinds of fabrication methods have been invented, however, existing technologies still cannot provide a satisfyng solution with both excellent performances and easy processing. Traditional ion doped optical waveguides have poor light confinement, while the newly emerged etching and precise machining techniques are still under developing. Searching for new fabrication methods for LiNbO₃ waveguide devices is a meaningful pursuit of both academic and practical value.</p> <p>In this study, a novel fabrication technique for LiNbO₃ waveguides has been proposed and realized. Through the combination of proton-exchange and precise diamond blade dicing, the annealed proton-exchanged (APE) LiNbO₃ ridge waveguides with low propagation loss and single transmission mode have been fabricated for both 1550 nm and 1064 nm wavelengths. The results have shown good agreements with theoretical simulation. Based on the obtained data, a nonlinear second harmonic generation (SHG) wavelength converter has been fabricated using the APE ridge waveguide built on periodically polled MgO:LiNbO₃ (PPMgLN) substrate. Test results have shown remarkable improvements comparing with traditional waveguide structures.</p> <p>Although there are remaining problems need to be solved, the fabricated waveguides have demonstrated great potentials for various optical applications. Based on this platform, mid-infrared generation by difference frequency generation (DFG), compact blue laser via SHG, high-speed optical modulators and many other useful devices can be built. Not all of them have been fully exploited yet.</p>