DESIGN AND CHARACTERIZATION OF TRAVELING-WAVE OPTICAL MODULATORS OF LINBO3 THIN-FILM WAVE-GUIDES GROWN BY LIQUID-PHASE EPITAXY

Using the liquid phase epitaxial growth (LPE) method, an LiNbO3 thin-film optical waveguide was formed on an LiTaO3 substrate with MgO added at 5 mol percent. This is channelized by Ar plasma etching so that a ridged waveguide is created. The TM mode optical propagation loss of this waveguide is 1.2 dB/cm at wavelengths of 1.55 mu m and 0.83 mu m. By means of this waveguide, a Mach-Zender-type optical intensity modulator was designed. The operating voltage was compared with that in a modulator designed with a Ti-diffused LiNbO3 waveguide. It was found that the electrooptic effect was approximately equal. Further, in the optical intensity modulator formed with traveling wave electrodes, the operating voltage was 4.6 V and the optical 3-dB bandwidth was more than 6.5 GHz in the frequency measurement at a wavelength of 1.55 mu m.