Mid-Infrared Characteristics of Metal/Insulator/Metal Tri-layer Structures Using Rectangular Metallic Patch Array as Top Layer and Polarized Multi-Spectral IR Thermal Emitters

本文在實驗及理論上探討以正方形金屬片陣列為上層之金屬/介電質/金屬三層結構中紅外頻段之光學特性。實驗數據顯示，當正方形金屬片尺寸增大時，結構中之侷域表面電漿模態波長會因而紅位移，且模態間距會減小。此結構所具之侷域表面電漿模態擁有如同線性天線角度圖案之反應，此特性可應用於製作廣角度之熱紅外線光源或光偵測元件。另一方面，實驗上觀察到經由調整正方形金屬片之間距造成的侷域表面電漿強度改變，及光柵耦合表面電漿/侷域表面電漿子之共存及耦合現象，可利用於此結構設計之最佳化。此外以長方形金屬片陣列為上層之金屬/介電質/金屬三層結構作為熱紅外線光源之熱輻射特性能在頻譜上產生更多模態。因對應侷域表面電漿子之方向不同，各模態均擁有特定之極化。將此元件與偏振片合成，可製成可選擇之多頻段熱紅外線光源。The characteristics of surface plasmon polaritons (SPPs) in metal/insulator/metal (MIM) structures using square patch arrays as top layers in the mid infrared region have been studied theoretically and experimentally. By tuning the size of square metallic patches, the shifts of peak positions and mode spacing variations of localized surface plasmon polaritons (LSPPs) have been investigated. The angular pattern of the LSPP modes has provided an excellent method to design wide-angle illumination or light-sensing devices. Besides, the effect on dispersion relation of material dispersion and changing of distances between metallic patches has been investigated. The effect gives a guideline to optimize the performance of the structure. Another structure using rectangular patch arrays as top layers of MIM structures has been discovered to possess multi-spectral and polarization response in thermal radiation. Integrate the structure with a rotatable polarizer, the system can serve as a peak-switchable IR thermal emitter