Study Of Proton-Exchange LiNbO₃ Single-Y Phase Modulator

With optical network and optical communication development, the demand for high performance and low price optoelectronic devices is larger and larger. LiNbO3 modulators have been firmly established in fiber-optic transmission and information processing systems for their advantages.LiNbO3 modulator waveguides have been traditionally fabricated by indiffusion of Ti. But an alternative simpler method is through the proton exchange (PE) process at lower temperature. PE waveguides exhibit larger increment of the index and lower waveguide loss than Ti indiffusion waveguides. However, PE waveguide devices haven't been fully mature.In this thesis, we described the structure characteristics, the proton concentration, and the refractive index distribution of the PE LiNbO3 waveguides. Then We analyzed the mode characteristic of the waveguides' mode through 3D-FDBPM. On the base, we designed the waveguides' structure and fabrication parameter.And in the design of symmetric Y-branch of Proton-Exchange S ingle-Y Phase LiNbO3 Modulaor, we used finite difference beam propagation method to analyze and compare the optical transmission lossof different S-bend Y-branch. On the basis of the analysis and compare, we designed the least length of S-bend Y-branch to decrease the transmission loss when the space between the outport is 250jjm.we also analyzed thoroughly dependence of half-wave voltage and bandwidth on the width, the length of modulator's electrodes and the gap between two electrodes. Then we optimized the structure of electrodes.On the basis of the theoretical analysis and design, we brought forward a method of fabricating technique for our laboratory, and we finished the fabrication of Proton-Exchange LiNbOa phase modulator. Because of the limitation of the measuring condition, in the thesis we had only measured some characteristics of the phase modulator: channel waveguides' loss coefficient is 0.22dB/cm, the split-ratio is 52/48 and half-wave voltage is <5V. Other performance will be measured after the device is packaged.