利用超穎材料和多孔微結構實現被動太赫茲元件之研究

Abstract

在光學領域中，傳統的光學元件，包括濾波器、吸收器和感測器，通常需要經過繁複且耗時的製程製作。然而，由於超材料具有卓越的特性，可以透過圖形設計實現其功能。在太赫茲波段的應用中，超材料工作頻段的可調製性引起了廣泛關注。此外，於太赫茲波段下所設計超材料的晶胞大小尺寸可以透過成熟的黃光微影製程實現，有助於改善太赫茲波段下光學應用的不足。本論文主要分為三個部分。第一部分探討了利用電控方式調製石墨烯帶，並結合多個方形環組成的超材料結構，形成太赫茲濾波器。透過調整方形環的尺寸，實現了多頻段濾波功能。此外，透過施加偏壓於石墨烯帶，能夠改變石墨烯的費米能階，進而將多頻太赫茲濾波器調整為單頻濾波器，可作為開關，對於6G通訊波段的發展具有潛在應用價值。第二部分著重於設計超材料作為超寬頻太赫茲吸收器，其在2.95至4.96 THz頻率範圍下表現出高達90 %的吸收率。同時，結合電控方式調製石墨烯，使吸收器的吸收頻段藍移，最高吸收頻率可達5.97 THz。值得注意的是，當改變入射角時，吸收體在大範圍的角度下仍能保持優異的吸收性能，表明此吸收器對於入射角具有不敏感性，有望實際應用於太赫茲偵測器。第三部分將太赫茲超材料感測器與多孔材料結合，用於氣體感測器。以可吸收一氧化氮之薄膜為例，利用鈣鈦礦結構鈦酸鋅與還原氧化石墨烯氣凝膠形成多孔材料，與超材料整合成超材料氣體感測器進行量測。在室溫下對於50 %的一氧化氮具有16.4 %的響應，且對不同氣體的具有高度選擇性，將實現室溫下以非接觸式氣體量測提供的可能，有助於生物醫學與穿戴式裝置的發展。第四部份將利用太赫茲超材料檢測極性液體，超材料上放置的目標材料達到一定厚度時，共振頻率變化飽和。為了有效利用超材料進行量測，需要考慮目標材料的光學特性，評估其可適用的最大厚度。超材料研究使得對薄膜介電常數深入研究成為可能，在此無需耗費大量材料。擴大檢測範圍允許深入研究各種極性液體對THz波的高度吸收的介電特性。這項研究有望克服THz波受極性液體吸收的限制，並在生物樣本檢測方面取得實質進展。總結而言，本論文致力於不同種不同太赫茲元件的開發，包括電控調製石墨烯超材料濾波器、具廣角不敏感吸收性的石墨烯超材料吸收器，以及高度選擇性的一氧化氮氣體感測器，與液體感測器。這些應用驗證了超材料在太赫茲波段的獨特光學特性，對太赫茲波段的應用將產生深遠的影響。In the field of optics, traditional optical components such as filters, absorbers, and sensors often require complex and time-consuming fabrication processes. However, metamaterials, with their exceptional properties, offer functional realization through graphical design. In the application of terahertz (THz) waves, the tunability of metamaterials in the working frequency range has gained widespread attention.This paper is organized into four main sections:Investigation of a graphene-based metamaterial for THz filtering, achieved by electrically modulating graphene ribbons within a structure composed of multiple square rings. Adjusting the sizes of these rings enables multi-band filtering, and applying voltage to the graphene ribbons facilitates the transformation from multi-band to single-band filtering, demonstrating potential applications in 6G communication.Design of a metamaterial as a broadband THz absorber, achieving up to 90% absorption in the 2.95-4.96 THz frequency range. Modulating graphene allows for the blue-shifting of the absorber's absorption band, reaching a maximum frequency of 5.97 THz. The absorber maintains excellent performance over a wide range of incident angles, indicating potential applications in THz detectors. Integration of a THz metamaterial sensor with porous materials for gas sensing. Utilizing a thin film capable of absorbing nitrogen dioxide, the sensor combines perovskite-structured zinc titanate and reduced graphene oxide aerogel to form a porous material integrated with the metamaterial sensor. Thesensor exhibits a 16.4 % response to 50 % nitrogen dioxide at room temperature, demonstrating high selectivity for different gases and offering possibilities for non-contact gas measurements in biomedical and wearable devices.Utilization of THz metamaterials for the detection of polar liquids. Resonant frequency saturation occurs when the target material on the metamaterial reaches a certain thickness. To optimize measurements, consideration of the optical properties of the target material and assessment of the maximum applicable thickness are necessary. This research allows for in-depth exploration of the dielectric constants of thin films without excessive material consumption, overcoming limitations posed by strong absorption of THz waves by polar liquids.In summary, this thesis focuses on the development of various THz components, showcasing the unique optical properties of metamaterials and their profound impact on THz applications.