| The field of communications has recently become more important due to the demands for exchange of increasingly larger quantities of information. Optical communication has attracted many scientists and engineers because its carrier wave has a frequency several orders higher than the conventional electrical carrier wave frequency. It is essential to develop faster way of modulation in order to take full advantage of the broadband nature of optical communication. Semiconductor EA modulator and LiNbO3 EO modulator are commonly used these days in spite of their own drawbacks. Lower driving voltage, broader bandwidth, and noise-free modulator are always welcome to optical communication industry. BaTiO3 is one of the prospective materials to achieve these goals since it has much stronger electrooptic effect than LiNbO3 does. However, its application to EO modulation was very limited owing to its availability. It is hard to make sufficiently large bulk BaTiO3 crystal. Recently size limitation has been overcome, thanks to thin film growth technique. In addition, heteroepitaxial BaTiO 3 on MgO has large index of refraction contrast, which will provide stronger optical mode confinement along the vertical direction.; This dissertation is concerned with developing next generation EO modulator based on epitaxially grown BaTiO3 on MgO. Basic theory has been reviewed in Chapter 2. EO modulator fabrication is presented in Chapter 3. First, geometrical dimensions are determined by calculation. Thin film growth and characterization section follows it. Optical waveguide processes and gold electrodes deposition processes are explained in detail later. Chapter 4 is devoted to optical and electrical measurements of the BaTiO3 modulator. DC modulation experiments confirm that the modulation results from electrooptic effect. Vπ*L was measured with full modulation, low frequency measurement. Its broadband response was measured by small signal measurement. |
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