A ridge-type Mach-Zehnder modulator on X-cut LiNbO3 is fabricated by wet etching with proton-exchange pretreatment. Experimental results show that, with the assistance of the ridge structure, the drive voltage of the proposed modulator is reduced. The enhancement of overlap integral caused by ridge structure is also validated from numerical simulation. Moreover, an improved design to further reduce the drive voltage of the ridge-type Mach-Zehnder is proposed by a proper placement of waveguide relative to the electrode.
Shih-Jung Chang, Ching-Long Tsai, Yih-Bin Lin, Ju-Feng Liu, and Way-Seen Wang, "Improved Electrooptic Modulator with Ridge Structure in X-Cut LiNbO3," J. Lightwave Technol. 17, 843- (1999)