Thermal stability of ion implanted LiTaO3 and LiNbO3 optical waveguides

Ion implantation forms optical waveguides in both LiNbO3 and LiTaO3 but in order to employ these in device applications one must be able to minimise barrier losses and absorption losses by using multiple energy implants and by annealing colour centres respectively. This requires a knowledge of the refractive index profile behaviour both as a function of dose and as a function of subsequent annealing. The paper reports mode measurements on a variety of waveguides formed by He+ ion implantation with different dose levels, ion energies and implant temperatures, and their subsequent isochronal anneal. Refractive index profiles are deduced using different wavelengths and index orientations, and the growth and recovery curves of the nuclear and electronic regions are compared for the two materials. (orig.)