Theoretical modeling and experiment of refractive index change in He+ ion-implanted KTP waveguide

A theoretical model is presented to explain the refractive index change in the ion-implanted KTP waveguide, which includes respective contributions of spontaneous polarization, molar polarization and molar volume, and photoelastic effect. Numerical calculations of refractive indices along different crystalline orientations (X, Y, and Z) as a function of the lattice damage level, determined by Rutherford back-scattering/channeling technique, are performed based on the results from a set of z-cut KTP crystals implanted by 300 keV He+ ions in doses ranging from 4×10(16) to 8×10(16) ions/cm2. The theoretical results show consistency with the experimental data. To our knowledge, this is the first model to comprehensively describe the ion-implanted KTP planar waveguide.