Preparation Of BTO Thin Films And Basic Research On Its Modulator Applications

The new generation of optical networks require high-performance signal processing waveguide modulator, and high performance electro-optic waveguide material is a prerequisite for the production of high performance modulator. Barium titanate(BTO) film materials have excellent electro-optical characteristics and compatibility of the substrate, it also can be highly integrated. With the development of microelectronics processing techniques, BTO film materials have important applications in the aspects of high-speed electro-optical device. In this paper, the preparation, experimental tests and modulator design of BTO films were studied. Based on the successful preparation of BTO film, we’ll achieve high-speed optical signal modulation by designing the modulator waveguide structure.We prepared BTO films by using the sol-gel method. The effects of spin coating BTO thin film layers on the thickness of the sample were discussed, and we optimized the process of preparation by analyzing the surface situation. The effect of spin-coating and drying parameters of temperature on the film thickness and quality were also studied, then the optimal process parameters to prepare high quality BTO films were achieved.We analyzed the influence of different annealing temperatures on the performance of thin-film crystal by using X-ray diffraction method, and obtained the optimal crystallization temperature was 700℃. A test system for measuring the electro-optic coefficient of BTO films was also set up. By using simple reflection technique, we got electro-optic coefficient was 87.5 pm/V at 533 nm wavelength. Waveguide structure was designed, the waveguide process was also studied through the laser direct-write lithography technology. We obtained lithography resolution of 10 μm, which satisfies the requirements of machining accuracy of waveguide.The ridge structure of BTO films’ effects on waveguide transmission mode were studied. Using the effective index method, single-mode propagation of the ridge waveguide was simulated to obtain waveguide structure parameters satisfying the single-mode transmission condition. Optimized BTO film inside and outside the high ridge waveguide were 600 nm and 300 nm, respectively, and the width should be less than 1μm. We designed the Y-branch type, directional coupler type two different beam structure of Mach-Zehnder type electro-optical modulator. The influence of structural parameters, such as the waveguide curvature radius of the bending, the length of the beam splitter to the optical signal transmission was studied. Finally we got the best structure parameters and provided a reference for device fabrication.