Low-temperature annealing of ion-implanted KNbO3 waveguides for second harmonic generation

Abstract

KNbO3 is a very attractive material for frequency conversion from the near-infrared into the blue.1,2 Results on second harmonic generation (SHG) experiments in KNbO3 waveguides formed by ion implantation were reported in Ref. 3. Implantation of MeV He+ ions into KNbO3 leads to the formation of a barrier layer with decreased refractive index a few microns below the surface defining a barrier waveguide. The incident ions loose energy by inelastic scattering with electrons and ions of the target. Ionic collisions are assumed to lead to permanent lattice damage, e.g., vacancies and interstitials. According to TRIM calculations the density of vacancies due to collision events in the waveguiding region is expected to be on the order of 2 X 1020 cm-3 (2600 ppm). Thus the creation of absorption centers (point defects, e.g., vacancies) in the waveguide is inherently related to the formation of the barrier waveguide itself.