Mach-Zehnder modulators with lithium niobate ridge waveguides fabricated by proton-exchange wet etch and nickel indiffusion

Mach-Zehnder ridge waveguide modulators on c/sup +/-LiNbO₃ by proton-exchange wet etch and nickel indiffusion are fabricated for the first time. Modulators operating at 0.633 μm and 1.31 μm are both produced, and the half-wave voltages are measured to be 4 V and 22.5 V, respectively, for an electrode length of 6 mm. The extinction ratios are 14 dB and 13.2 db, respectively, and can be improved by forming the ridge structure only at the electrode interaction region instead. These results make the wet-etched LiNbO₃ optical devices promising to take over the dry-etched ones in the near future.