A novel self-aligned fabrication process for Ni : LiNbO3 ridge waveguides has been proposed. By using the self-aligned trilayered structure composed of Ni/Ti/Si, the fabrication process is significantly simplified, and takes advantage of suppression of the unwanted planar waveguides and high-coupling efficiency to a single-mode fiber as compared to the conventional processes. Detailed investigations into the characteristics of the ridge waveguides have also proved to be informative under different fabrication parameters. Moreover, the novel self-aligned fabrication process was applied to fabricate a ridge waveguide Mach-Zehnder modulator. The measured half-wave voltage and extinction ratio were 20.5 V and 12 dB (@ 1.3 \mum), and were 4.2 V and 8 dB (@0.6328gm).
Wen-Ching Chang, Chao-Yung Sue, Hung-Ching Hou, Shih-Jung Chang, and Pei-Kuen Wei, "A Novel Self-Aligned Fabrication Process for Nickel-Indiffused Lithium Niobate Ridge Optical Waveguides," J. Lightwave Technol. 17, 613- (1999)