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

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Abstract
Mach-Zehnder ridge waveguide modulators on c/sup +/-LiNbO/sub 3/ by proton-exchange wet etch and nickel indiffusion are fabricated for the first time. Modulators operating at 0.633 /spl mu/m and 1.31 /spl mu/m 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 LiNbO/sub 3/ optical devices promising to take over the dry-etched ones in the near future.