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The purpose of the thesis is to design and fabricate the directional couplers in integrated optics. Furthermore, we propose a novel fabrication process of ridge waveguide. The devices were first fabricated by Ni-indifussion on LiNbO3 at 900℃ for 120 minutes. Then, proton exchange (PE) and wet etching technique was used to form ridge structure. Finally, the aluminum electrodes were deposited by evaporation.
In this thesis, we propose the directional coupler with different structures including the ridge waveguides, the buried-type channel waveguides and the mixed-type waveguides. In order to optimize the performance of the devices we vary the lengths of electrodes and the gap between electrodes. Therefore, the switching voltage was measured. From the results of experiment we compare the characteristics of these structures.
We successfully fabricate the directional coupler by nickel indiffusion at the first time. A comparison of voltage-length products between the buried-type and mixed-type directional coupler shows that the mixed-type waveguide can have an improvement of as large as 40%. As to the novel fabrication process of ridge waveguide, we successfully develop a simple and efficient method with only one photolithography process. We also prove the practicability of this novel process by fabricating the directional coupler with good performance.
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