石墨烯與高熵合金薄膜於表面電漿高反射結構及生物感測之應用
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2022
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近幾年以來,表面電漿在光學元件設計應方面逐漸受到矚目,其強光場侷限性、較小的模態體積及打破繞射極限的能力,為它在微奈米元件領域中占有一席之地。本論文主要分為兩個部分,第一部分為使用高熵合金薄膜製成的表面電漿高對比度光柵高反射結構,使用有限元素法進行模擬。利用表面電漿的強光場侷限性,以及高對比度光柵利用環境的低折射率與光柵的高折射產生與一般光柵不同的效果,產生針對於兆赫波的高反射率。高對比度光柵本身是一種亞波長結構,利用高折射率材料做週期性的排列,再以相對低折射率的環境包覆光柵形成的光學元件,雖然結構與一般光柵相似,但能夠利用guided-mode resonance的理論產生所謂的橫向傳播,產生高反射的效果。第二部分為使用紅外增強吸收光譜結合石墨烯的表面電漿可調變生醫感測器,我們同樣使用有限元素法進行模擬。利用表面電漿的強光場侷限性及打破繞射的能力,將光場侷限於我們設計的石墨烯表面微奈米結構以增強紅外光與待測物質間的交互作用。而石墨烯在元件中所扮演的角色還有另一個作用,除了提供取代傳統金屬層與介電質層產生表面電漿的交互作用以外,也提供了元件的電性可調變之能力,能夠在不改變元件設計的情況下增加其量測範圍,提升其對於不同待測物的感測能力。我們所設計的兩種元件皆利用表面電漿在材料表面的高度侷限能力,並使用兩種不同材料對其進行設計,此研究結果預期對於為奈米尺度的表面電漿光學元件是有益的。
In recent years, surface plasmon has attracted attention in the design of optical components. Its strong light field limitation, small modal volume and ability to break the diffraction limit have given it a place in the field of micro-nano components.This research is mainly divided into two parts. The first part is a surface plasmon high-contrast grating and high-reflection structure made of high-entropy alloy thin films, which is simulated by the finite element method. Taking advantage of the strong light field limitations of surface plasmons, and high-contrast gratings utilize the low refractive index of the environment and the high refractive index of gratings to produce a different effect than general gratings, resulting in high reflectivity for Terahertz waves. The high-contrast grating itself is a sub-wavelength structure, which uses high-refractive-index materials for periodic arrangement, and then wraps the optical elements formed by the grating with a relatively low-refractive index environment. Although the structure is similar to the general grating, the theory of guided-mode resonance can be used to generate lateral propagation, resulting in the effect of high reflection.The second part is a surface plasmon tunable biomedical sensor using infrared enhanced absorption spectroscopy combined with graphene, which is also simulated by the finite element method. Taking advantage of the strong light field limitation of surface plasmon and the ability to break diffraction, the light field is limited to the graphene surface micro-nano structure we designed to enhance the interaction between infrared light and the substance to be tested. And graphene has another role in the device, in addition to providing a replacement for the interaction between the traditional metal layer and the dielectric layer to generate surface plasmons, it also provides the ability to adjust the electrical properties of the device, which can increase its measurement range without changing the design of the device, and improve its sensing capability for different objects to be tested. Both devices we designed take advantage of the highly confinement capabilities of surface plasmons and are designed using two different materials, and the results of this study are expected to be beneficial for nanoscale surface plasmonic optical devices.
In recent years, surface plasmon has attracted attention in the design of optical components. Its strong light field limitation, small modal volume and ability to break the diffraction limit have given it a place in the field of micro-nano components.This research is mainly divided into two parts. The first part is a surface plasmon high-contrast grating and high-reflection structure made of high-entropy alloy thin films, which is simulated by the finite element method. Taking advantage of the strong light field limitations of surface plasmons, and high-contrast gratings utilize the low refractive index of the environment and the high refractive index of gratings to produce a different effect than general gratings, resulting in high reflectivity for Terahertz waves. The high-contrast grating itself is a sub-wavelength structure, which uses high-refractive-index materials for periodic arrangement, and then wraps the optical elements formed by the grating with a relatively low-refractive index environment. Although the structure is similar to the general grating, the theory of guided-mode resonance can be used to generate lateral propagation, resulting in the effect of high reflection.The second part is a surface plasmon tunable biomedical sensor using infrared enhanced absorption spectroscopy combined with graphene, which is also simulated by the finite element method. Taking advantage of the strong light field limitation of surface plasmon and the ability to break diffraction, the light field is limited to the graphene surface micro-nano structure we designed to enhance the interaction between infrared light and the substance to be tested. And graphene has another role in the device, in addition to providing a replacement for the interaction between the traditional metal layer and the dielectric layer to generate surface plasmons, it also provides the ability to adjust the electrical properties of the device, which can increase its measurement range without changing the design of the device, and improve its sensing capability for different objects to be tested. Both devices we designed take advantage of the highly confinement capabilities of surface plasmons and are designed using two different materials, and the results of this study are expected to be beneficial for nanoscale surface plasmonic optical devices.
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表面電漿, 高熵合金, 高對比度光柵, 兆赫波, 石墨烯, 生醫感測器, 有限元素法, Surface plasmons, high-entropy alloys, high-contrast gratings, Terahertz waves, graphene, biomedical sensors, finite element methods