The lattice expansion, damage effect and propagation loss of KTiOPO4 waveguides formed by ion implantation

Abstract

We investigated the damage effect on the refractive index as well as the lattice expansion induced by C 3+ ion implantation into KTiOPO 4 crystals. A KTiOPO 4 channel waveguide was formed by area-selective 6.0 MeV C 3+ ion implantation at a fluence of 5×10 13 ions/cm 2 using photoresist masking, and planar waveguides were formed by ion implantation with 6.0 MeV C 3+ ions at fluences from 8×10 12 ions/cm 2 to 6×10 14 ions/cm 2 . The propagation loss of the KTiOPO 4 planar waveguides at 633 nm fabricated at fluences of 2×10 13 ions/cm 2 and 5×10 13 ions/cm 2 after annealing is as low as 0.38 and 0.54 dB/cm, respectively. Prism coupling and refractive index profile reconstruction using the reflectivity calculation method were used to investigate the anisotropy of the refractive indices in the KTiOPO 4 waveguides region before and after annealing. The lattice expansion induced by ion implantation was investigated by combining X-ray rocking curves with atomic force microscopy. Rutherford backscattering spectrometry and channeling was applied for damage analysis, and the relationship between effective refractive index and relative defect concentration was studied.