Diffusion characteristics study of locally Er-doped noncongruent, Li-deficient Ti:Er:LiNbO₃ strip waveguide

Locally Er³⁺-doped noncongruent, Li-deficient Ti:Er:LiNbO ₃ strip waveguide was fabricated with a technological process in sequence of preparation of Li-deficient LiNbO₃ substrate using Li-poor vapor transport equilibration (VTE), Er³⁺, and Ti ⁴⁺ diffusion in wet O₂. The Li₂O content change was evaluated from the measured birefringence. The Ti⁴⁺ and Er ³⁺ profile characteristics in the waveguide were studied by secondary ion mass spectrometry. The results show that the VTE and subsequent Er ³⁺ diffusion procedures resulted in totally ∼0.8 mol% Li ₂O content reduction. The Ti⁴⁺ profile follows a sum of two error functions in the width direction and a Gaussian function in the depth direction of waveguide. The Er³⁺ profile follows also a Gaussian function. At 1130 °C, the Ti⁴⁺ surface/depth diffusivity and surface concentration are 8.5 ± 1.3/1.98 ± 0.06 μm ²/h and ∼7 mol%, respectively, and the Er³⁺ diffusivity and surface concentration are (12.8 ± 0.3) × 10 ^-2 μm²/h and ∼0.6 mol%, respectively.