| Optical communication technologies have been developed rapidly in recent years. Optical switches are one of the most important components for constructing transparent and flexible communication networks. Planar lightwave circuits (PLC) based optical switches attract more and more interests due to their high controllability, excellent reliability, low cost and mass producibility. Recent works on highly integrated thermo-optic PLC-switches have been reviewed. In this thesis, we proposed a novel Mach-Zehnder interferometer (MZI) type thermo-optic switch based on SU8-Silica hybrid waveguide structures. Such hybrid SU8-Silica waveguide structures combine the advantages of the low propagation loss of the silica waveguides and the high thermo-optic effect of SU8. Due to the high thermo-optic coefficient of SU8, the length of the transmission arm can be dramatically reduced. Thus, optical switches with high compactness and low power consumption can be realized.Firstly, the fundamentals of the optical waveguides are briefly reviewed. Single mode condition, bending loss of the hybrid SU8-Silica waveguides have been analyzed. The coupled mode theory is introduced. A typical numerical simulation method-beam propagation method (BPM) is also introduced.Then, the MZI based SU8-Silica hybrid thermo-optic switch has been analyzed and optimized. Both the splitter and the combiner are based on multimode interference (MMI) couplers. For the purpose of reducing the coupling loss between the silica waveguide and SU8 waveguide, we optimize the SU8 waveguide dimension parameters by using the overlap integral.3D-BPM is utilized to verify the design. The two methods give the same result that the coupling loss between waveguides is about 0.81. Finally, we fabricated the device according to the simulated results. The SU8-silica hybrid waveguide can be realized by using overlay exposure. The measurement results show good agreements with the simulated ones. |
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