Recrystallization and refractive index profiles of titanium-implanted optical waveguides in LiNbO3

Abstract
Y‐cut LiNbO3 single crystals have been implanted with 200‐keV Ti+ at doses up to 4.0×1017 Ti/cm2. 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/m3 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.

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