Model of refractive-index changes in lithium niobate waveguides fabricated by ion implantation

Abstract

A model is presented to explain the refractive-index changes in the ion-implanted $\mathrm{Li}\mathrm{Nb}{\mathrm{O}}_{3}$ waveguides that indicates that the lattice damage may be the main factor for the refractive-index changes. The model indicates that a slight enhancement may occur for the extraordinary refractive index in the ion-implanted $\mathrm{Li}\mathrm{Nb}{\mathrm{O}}_{3}$ waveguides with lattice damage ratios of less than 65%, and a maximum positive change $(\ensuremath{\Delta}n=0.0338)$ occurs at a damage ratio of 33%. The model explains both the positive refractive-index changes observed in waveguides formed using $500\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$ ${\mathrm{Si}}^{+}$-ion implantation and the refractive-index changes observed in ${\mathrm{He}}^{+}$-ion-implanted waveguides.