Design and Fabrication of Novel Ridge Guide Modulators in Lithium Niobate

A thorough theoretical analysis of Mach-Zehnder-type ridge guide modulators has been performed in this paper. A novel electrode/waveguide structure was identified, yielding low driving voltages for high bandwidth operation. Based on this design, the fabrication of improved modulators was developed, introducing various novelties: low-loss Ti-indiffused wet-etched ridge guides in LiNbO₃, a complete ridge guide interferometer, and a specific electrode structure to be used with ridge interferometers. The operation of the modulator was demonstrated, yielding V _pi = 2.14 V and V _pi L = 5.35 Vmiddotcm at low frequencies and an on-off extinction ratio of 20 dB.