| Summary: | 碩士 === 國立臺灣大學 === 應用力學研究所 === 103 === Localized surface plasmon resonance (LSPR) is the oscillation of electron confined in the metallic nanostructure. In sensing application, high sensitivity can be realized in small surface due to the nature of LSPR. Contrast to the sensing system based on surface plasmon resonance (SPR) require large propagating surface, the system based on LSPR can be miniaturized. A high aspect ratio U-shaped cavities structure was proposed recently. The LSPR coupled to the cavity mode in the structure can strongly trap the light and have superior sensing performance. It can also work in a few cavities which meet the purpose of miniaturization in LSPR based system. However, this mode can only be excited by the oblique incident light. Consider the U-shaped cavities as an array of 2-D cantilever beams, the interaction between the vibrational mode of the cavities and the light becomes an interesting topic.
In this thesis, the optical behaviors in the vibration modes of the U-shaped cavities are numerically investigated. The LSPR coupled to the cavity mode and its higher order mode can be excited by the normal incident light in the active U-shaped cavities. The light confinement and the sensing performance are related to the vibrational amplitude of the cavities. The sensing performance is higher than the original design in certain amplitude. In the active cavities with oblique incident light, the sensitivity is increased as the vibrational amplitude increase in higher order vibrational modes.
In practice, the cavities are designed to be driven by the Rayleigh surface wave which is generated by the pairs of the interdigital transducers. A 2-D phononic crystal is also adopted. The vibrational amplitude of the cavities can be enhanced to about 3 times by using phononic reflective gratings.
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