Depth dependence of radiation damage in Li+-implanted KTiOPO4

KTiOPO4 single crystals were irradiated at 100 and 295 K with 1 MeV Li+-ions at an ion fluence of 3 x 10(15) cm(2) and subsequently annealed at 620 and 720 K. The irradiated layers were analyzed by means of various complementary methods (Rutherford backscattering spectrometry, cross-sectional transmission electron microscopy, electron-energy loss spectroscopy, m-line spectroscopy). The complex damage structure produced consists of a slightly damaged. covering layer, a transition layer with amorphous clusters and a buried amorphous layer the thicknesses of which depends on the irradiation temperature. The depth distribution of the damage is in accordance with the distribution of the nuclear energy deposition. The buried amorphous layer possesses a significantly reduced refractive index thus acting as a refractive index barrier for waveguiding. Upon thermal treatment, defects anneal mainly in the covering layer, the barrier height is preserved and the slope of the barrier becomes steeper. The attenuation of light in the waveguide after thermal treatment is as low as 1.5 dB cm(-1). (C) 2002 Published by Elsevier Science B.V.