| 摘要: | 自1990年代中期以來﹐科學家投入相當程度的注意力在開發具有非線性吸收特性的材料與其相關的應用技術上。此類材料在光子學及生醫光(電)子學上擁有許多不同的應用潛力﹐包括﹕光學功率限幅器､頻率轉換器､全光開關､三維光學記憶體､三維微結構製造､光動力治療､非破壞性生物檢測與追蹤以及非破壞性生物顯相技術等。由於目前已商業化的化合物皆無較強的非線性吸收性質以敷上述各項應用所需﹐因此必須藉由分子設計並透過合成來製備高效能之非線性吸收材料以滿足各項應用開發相關技術的需求。為有效達成此一目的﹐在基礎研究上必須致力於有系統性地透過有機合成以微調分子的官能基及結構﹐並利用可靠的光學量測技術來探究這些分子的非線性吸收特性。經過約莫15年的努力﹐材料化學家從分析各類型的分子結構與其非線性吸收性質間的相關性學習到若能有效地使分子在受光激發下於分子內產生較劇烈的電荷轉移便能有效地提高材料的非線性吸收能力。在這一個分子設計的大方向下﹐尚有許多細節有待科學家作進一步的探索﹐諸如﹕-電子非定域化範圍大小的影響､分子共平面性與分子對稱性的影響以及如何增加有效-電子數…等。這些問題的釐清都需要材料化學家與理論化學家攜手努力。基於上述考量，我們研擬了一個為期兩年的研究計畫並將其分為以下三項互有關聯之研究課題： [1] 分子設計及合成具有寬譜帶之非線性吸收特性的材料。 [2] 探索分子結構與其線性與非線性吸收性質間的關聯性。 [3] 不同時域光學功率限幅效能與分子結構間的關聯性探討。在此計畫中的材料的合成方面，我們預定發展兩類結構特性不同的分子系統：第一類為「含雜環及不同吸光中心之之多叉及樹枝型共軛染料分子」；第二類為「啞鈴型多叉及樹枝狀共軛染料分子」。由於目前我們已初步擁有適當的實驗條件來進行這一個計劃，所以這些新開發出來的材料將配合精密的光學儀器和量測技術作鑑定，由其中所得之研究結果將有助於我們對材料的分子結構與其非線性吸收行為間之關聯性有較深入的認識。同時，此項工作也有利於建立對材料的分子設計及應用有很大助益的分子資料庫。在這一個為期兩年的研究計畫中，我們將與本校超快雷射實驗室積極地合作並期待能籌組具同時監控雷射波長與脈衝時間寬度的較完善光學設施以期未來能進行更深入的時域相關性的研究。另一方面，我們也將繼續與國際合作者保持密切且互動的國際合作以便針對這些材料的非線性吸收光學性質進行多方面的探討。 Broad-band multi-photon absorbing materials are of significant interest to the academic community, industry, and military for numerous applications including optical power limiting, frequency up-conversion, IR to visible optical-optical conversion, 3D data storage, photodynamic therapy and noninvasive bio-imaging. The commercialized materials are not good candidates for these applications because they possess comparatively poor nonlinear absorption properties. Therefore, for the practical purposes, it is very important to develop and explore new multi-photon absorbing materials with strong optical nonlinearity coupled with enhanced structural flexibility, ease of processing, low cost and large-scale manufacturability. In order to approach this goal, well-defined structure-property relationships must be established. This requires an investigation of large number of different structures with systematically varied molecular structural parameters by reliable characterization methods. With the aid of two-photon-excited fluorescence (2PEF) and Z-scan techniques for the degenerate nonlinear absorption spectra measurement, it is possible to explore the dispersion of multi-photon absorbing of the studied compounds within a certain spectral range. The data obtained by these techniques provide very useful information for us to study the structure-nonlinear absorption property relationships. This two-year Proposal is composed of three correlative parts: I. Molecular Design and Synthesis of Broad-band Nonlinear Absorbing Dyes; II. Linear and Nonlinear Optical Properties Characterization and Structure-Nonlinear Absorption Property Relationship Studies; III. Investigation of The Connections Between Molecular Structures and Optical Power Limiting Properties in Nanosecond Regime In order to explore the structural effects on the linear/nonlinear absorption band-width, we intend to develop two classes of multi-branched/dendritic compounds for this study: (i) Novel heterocyclic units containing multi-chromophoric structures with star-shaped and dendritic geometries, (ii) Novel dumb-bell shaped dendritic structures. For nonlinear optical properties characterization, both the methods that utilize 2PEF at various time regimes to probe the spectral response of nonlinear absorption and Z-scan will be conducted. The study of optical power limiting properties is planned to be carried out under the irradiation of nanosecond laser pulses. This two-year continuous research involves multidisciplinary efforts including materials design, chemical synthesis, and optical properties characterization. In this research, we also aim to build up a more comprehensive optical set-up in order to simultaneously monitor/control the laser wavelengths and pulse width during the experiments in various time-domain. At the same time, we will continuously work with our domestic and international collaborators very closely to explore other nonlinear optical properties which may have potential for the applications.The detail works involved in this Proposal and the plan of carrying out the proposed research on the yearly basis is described in detail in the text body of this Proposal. 研究期間：9908 ~ 10007 |
