RECRYSTALLIZATION AND REFRACTIVE-INDEX PROFILES OF TITANIUM-IMPLANTED OPTICAL WAVE-GUIDES IN LINBO3

Y-cut LiNbO3 single crystals have been implanted with 200-keV Ti+ at doses up to 4.0×1017 Ti/cm 2. The annealing behavior has been studied with implantations performed at 77, 300, and 620 K. The amorphous surface layers have been annealed at 1273 K in a wet oxygen atmosphere for 2 to 8 h to achieve epitaxial regrowth. Channeling and mode spectroscopy have been applied to investigate the regrowth process. Refractive index profiles have been calculated with an inverse WKB algorithm. A maximum increase of 0.040 for the extraordinary and 0.019 for the ordinary refractive index was found at He-Ne wavelength (632.8 nm). This indicates a solubility limit of 3.3×1027/m 3 for Ti in LiNbO3. The annealing time to achieve perfect regrowth depends on the ion dose and irradiation temperature. Higher implantation temperatures yield dynamical annealing; thus, a shorter post-implantation anneal is required.