Reverse proton exchange for buried waveguides in LiNbO_3

Abstract

The reverse proton-exchange (RPE) process performed in different HxLi1-xNbO3 crystalline phases of proton-exchanged and annealed proton-exchanged LiNbO3 waveguides leads to remarkable optical and compositional modifications. Analysis of ordinary and extraordinary index profiles, correlated with concentration depth profiles in RPE samples subjected to different exchange and postexchange treatments, shows how buried-index optical waveguides in LiNbO3 with symmetric mode and reduced fiber–waveguide coupling losses can be realized.