| Summary: | 碩士 === 國立臺灣科技大學 === 電子工程系 === 104 === In 1969 S. E. Miller in Bell Labs proposed the concept of optical integrated circuits, which promoted extensive study on a variety of waveguide materials such as polymers, glass, and LiNbO3 in the 1970s,. The development of optical integrated circuits can be divided into three generations. The first is a conventional optics, the second is known as micro-optics and the third generation of this era is named as integrated photonics. However, silicon-on-insulator (SOI) is widely used in recent years for the high-speed and low-power electronic components. Because silicon owns a high refractive index besides the complementary metal oxide semiconductor (CMOS) compatible process, SOI based devices can significantly be reduced to a small foot print and becomes a popular platform in the optoelectronic integrated circuit developments.
In this thesis the biosensor is implemented using the waveguide coupled surface plasmon. The functions of FDTD (Finite Difference Time Domain) and FDM (Finite Difference Method), built in the commercial software of OmniSim and FIMMWAVE, are taken to simulate the surface plasmon effect under the variation of the metal thickness, plasma waveguide length and width.
There are three coupling approaches in surface plasmons: grating coupler, optical waveguide and prism. In this thesis a silicon based optical waveguide is utilized as the biological sensors through surface plasma polaritons. The main structure is to implement the surrounding metals on top of the silicon-wire waveguide. When the optical mode is interfered with the metal, a surface plasma wave will be induced in the interface between the metal and dielectric film, same as the other metal interfaces. At the end of the surface plasmon region, all the interference will be joined together and coupled to the silicon-wire. This mechanism is equivalent to the function of Mach Zehnder interferometer (MZI). The simulation results are showing that the sensitivity is up to 2891 nm/Refractive Index Unit (RIU) and the details will be further discussed. Due to the lithography limitation from the National Nano Device Laboratories(NDL), the silicon-wire width is chosen 450 nm and 3 μm for simulation verification.
A broadband Mach-Zehnder directional coupler (MZDC) is constructed by two directional couplers connected through a short delayed length. The new concept in this thesis is to use the surface plasmon interference, hybrid plasmon waveguide (HPW), with the short length to replace the decoupled region of MZDC. The HPW based MZDC could demonstrate the arbitrary splitting ratios, such as 50:50, 70:30, and 90:10, in the S and L bands.
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