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Formation of Optical Waveguide and Annealing Behaviour of LiNbO3 Implanted by 3.0-MeV Nickel Ions

The optically polished LiNbO3 crystal was implanted with 3.0 MeV nickel ions to a dose of 8×1014 ions/cm2. The implanted sample was orderly annealed at different temperatures for different times in air ambient. The waveguide properties before and after annealing were investigated. Dark modes were observed by the prism coupling technique. The reconstructed refractive index profiles were obtained with the reflectivity calculation method. With the fibre probe technique, the attenuation of the Ni-implanted barrier-confined waveguide was measured for the first time. The waveguide loss was reduced from 1.65 dB/cm to 1.19 dB/cm when annealing was at 300 degrees C for 30 min. With the annealing temperature increasing to 370 degrees C, only fewer broad dark modes were found. It is indicated that the lattice damage by implantation began to resume under this annealing condition. After annealing at 380 degrees C for 60 min, all the dark modes disappeared.