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Theoretical Investigation of Energy Transfer and Electron Transport in Photonic Nanostructures
|Contributors: ||NTOU:Institute of Optoelectronic Sciences|
|Issue Date: ||2011-06-28T07:06:41Z
|Abstract: ||摘要:在此兩年期之計劃中，我們將探討奈米光學結構中之光電物理過程．在第一年中， 我們將處理置於金屬奈米結構表面附近，或在光子晶體中之兩分子，或兩個量子點之間 的能量轉移．雖然分子間的電偶極交互作用可由庫侖定律來理解．根據量子光學，兩個 二能階原子之間的作用，是由輻射場作為中間媒介造成，且輻射場可由環境來改變．我 們將應用此一原則，至分子及量子點上，並將分子中之電子－振動偶合，及量子點中激 子與聲子交互作用考慮進來．在金屬奈米結構的表面附近，表面電漿在兩分子所在位置 提供很強的局部場．因此導致此二分子之間有很高之能量轉移率．在光子晶體中，由於 光子能帶間隙的形成，以致光子之局部狀態密度有些異常形式．因此兩分子之間交互作 用形式亦有異常行為．我們將計算共振螢光及分時光譜以使交互作用及能量轉移之效應 能突顯出來．並與實驗作比較． 在第二年中，我們將研究單量子點之電激發光及光電導性，在我們的考慮中，電極 部份是由兩個金屬奈米粒子構成．由於單光子源，在現階段之量子資訊發展上，是一非 常重要的環結．而單量子點之電激發光是一理想之單光子源．而光電導性則在光偵檢器 及太陽電池扮演重要角色．在這兩項研究中，我們主要關切的重點，是金屬顆粒的影響． 由於金屬表面電漿產生之局部場，量子點之發光率將大為提升，因此在量子點中，出現 雙激子之機率會大為降低．因此輻射光之光子較易呈現反群聚統計特性．而在單量子點 光電導性中，亦由於金屬顆粒的表面電漿的緣故，使光之吸收率大為提升．對此二主題， 我們將以非平衡格林函數的方法計算穿過單量子點之電流．在計算中，其他之相關效應 如金屬中之電漿與單粒子激發之交互作用及量子點中激子與聲子之交互作用亦將納入 考慮．計算之結果亦將與相關實驗比對．|
Abstract:In this two-year project, we will investigate optoelectronic process occurring in photonic nanostructures. Within the first year, we will focus on the energy transfer between two molecules or two quantum dots (QDs) located at the vicinity of a metallic nanostructure or embedded in a photonic crystal. Typical dipole-dipole interaction between molecules can be understood from point of view of electrostatics. According to quantum optics, however, interaction between two two-level atoms is mediated by the radiation field which can be changed radically by environmental condition. We will apply the same principles to molecules and QDs for which we will take into account vibronic coupling as well as exciton-phonon interaction respectively. Near the surface of metallic nanostructure, the surface plasmons provide strong local fields at the positions of the two molecules and thus effectively mediate the energy transfer process between them. In the photonic crystal, the novel local density of states for photon, due to the formation of photonic band gap, results in different features in the interaction potential between the two molecules. We will calculate resonance fluorescence and time resolved spectra in which the effects of the interaction and energy transfer between molecules can be manifested and the calculated results will be compared with experiments. In the second year, we will investigate the electroluminescence (EL) and photoconductivity (PC) of a single QD with electrodes consisting of two metallic nanoparticles. EL with a single QD is a preferred system to generate single photon source which is an essential ingredient for the development of quantum information technology, while PC is significant in the applications of photodetector and solar cell. For both EL and PC the effect of the metallic nanoparticles is the main point we are concerned with. Due to the local field provided by the surface plasmons of the metallic nanoparticles, the emission rate of photon from the QD is expected to be largely enhanced and the generation of biexciton state in the QD can be efficiently suppressed. Consequently, anti-bunching statistics of the emitted photon can be exhibited easily. To the PC, the exciton in the QD is strongly coupled to the plasmons and thus results in large cross section of absorption. For both EL and PC, we will use the nonequilibrium Green』s function method to calculate the tunneling current through the single QD, taking into account numerous other effects such as the interaction between plasmon and single-particle excitation in the metal and exciton-phonon interaction in QD. The findings in the calculation will be used to explain available experimental results.
|Appears in Collections:||[光電科學研究所] 研究計畫|
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