He+ implantation for waveguide fabrication in KTP and Rb:KTP

Abstract Z-cut flux grown KTP single crystals were implanted at room temperature with total He + ion fluences ranging from 3.2 × 10 15 to 3.2 × 10 16 cm −2 . The energy was varied between 250 keV and 5 MeV. All samples were furnace annealed at 250°C, 300°C and 350°C in normal atmosphere. By means of m-line spectroscopy the guided mode spectra as well as the refractive index profiles were determined. A dose-dependent decrease of the refractive index at the depth of maximum nuclear energy deposition down to values around Δ n =−0.14 was observed. The thickness of the near surface waveguides ranged from 0.6 to 23 μm and correlates well with the depth distribution of the nuclear energy deposition. Only waveguides formed with ion fluences above 1.3 × 10 16 cm −2 remained stable after annealing. An equivalent behaviour of the value and depth distribution of the refractive index is found for Rb-exchanged KTP after implantation. The formation of buried optical channel waveguides by He + implantation into Rb-exchanged KTP was demonstrated for the first time. The nearfield pattern and the transmittance of the waveguides were measured.