Study of Magneto-Optic Surface Plasmon Resonance Sensing Devices
| Autor: | Kuo-Hao Lee, 李國豪 |
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| Rok vydání: | 2012 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 100 This thesis studied the sensing properties with four different thin-film structure. The influence of sensing properties with magneto-optic (MO) layer/gold film structure, thickness ratio, and total thickness is discussed. Finally, the measurement setup of MO modulated surface plasmon resonance (SPR) sensing is established. In this study, we present a MO modulated SPR sensing system in the attenuated-total-reflection (ATR) configuration, which can be used to measure the concentration of analyte. The samples composed of a sensing region with Au film and a magneto-optically active layer with ferromagnetic materials are thermally evaporated on a glass. In simulation, the 4×4 Transfer Matrix Method is used. This calculation will find optimal structure parameters, the effect of MO layer/gold position and thickness ratio are discussed. Simulation results show that sensitivity can be enhanced by optimizing the structure parameters. In this application, the result of magneto-optical (MO) enhancement signal is extremely depending on the thickness of the ferromagnetic material. Transition metals such as Fe and Co exhibit the larger image part of complex refractive index (k), so that their absorption coefficients are higher than those of Au. Therefore, the choice of ferromagnetic material thickness is extremely significant. In addition, the position of ferromagnetic material must be adjusted in order to balance optical absorption and a high degree of MO activity. The thickness and position of films is changed to optimize the sensing property. During the sensing measurement, the alternate magnetic field as field-modulated and lock-in technique as MO signal record that can be determined by relation between the reflection intensity and refractive index change is used. In comparison with the conventional SPR sensing, that is based on changes in the optical properties at the sensing surface in passive, the MOSPR can be modulated actively by external field to improve sensing sensitivity. Finally, the sensitivity of MOSPR sensor is double enhanced compared to conventional SPR. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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