LITHIUM-NIOBATE RIDGE WAVE-GUIDES BY NICKEL DIFFUSION AND PROTON-EXCHANGED WET ETCHING

Lithium niobate ridge waveguides are fabricated by a combination of nickel diffusion and proton-exchanged wet etching technique. The nickel diffusion planar waveguide is carried out at 800 degrees C for 1.5 h and the ridge pattern fabrication process starts with a masked proton exchange to induce domain inversion in lithium niobate and then followed by etching away the exchanged area with a mixture of hydrofluoric acid (HF) and nitric acid (HNO3). The surface of wet etching ridge waveguide is very smooth as compared with those by the reactive ion etching, The simulated and the measured output intensity profiles of the ridge waveguides are found to be in good agreement.