Electrooptic Coefficient r₃₃ in Proton-Exchanged z-Cut LiTaO₃ Waveguides

LiTaO 3 TM-mode planar optical waveguides have been fabricated on a z -cut substrate through one-step proton exchange in benzoic acid below 250°C. The effective diffusion coefficient is measured as D = D 0 exp (- E a / k T ) with D 0 of 3.61×10 17 µm 2 /h and the activation energy E a of 1.82 eV. In the single-mode waveguides, the propagation loss is as low as 0.7 dB/cm at the light wavelength of 633 nm. The electrooptic coefficient in these waveguides is measured as 28.4±0.4 pm/V at 633 nm, and almost negligible electrooptic degradation is observed compared with the bulk LiTaO 3 .