| 摘要: | 電漿子近乎無繞射極限的特性使得光可被侷限於奈米尺度的空間中，而其純量特性如波長、強度、相位等得以被輕易地操控。然而，欲在奈米尺度操控光的偏振態仍是一大挑戰，被科學家們視為邁向全面操控光子與分子間交互作用的最後一哩路。恰如法拉第一百多年前對光的評註: “Polarised light is the most subtle and delicate investigator of molecular condition.”延續第一年成果，在本計畫中，我們將研究奈米尺度下偏振態操控及超掌性現象。期能結合奈米粒子與光波導結構產生單一超掌性電磁場及可分離掌性分子之光學力，進行鏡像異構物的分離。研究方法包含:電漿子寡聚體製作、超解析四波混合光源、基於圓錐折射之偏振測定、廣義多粒子米氏散射模擬、光流道技術等。目前理論模擬與實驗均有初步成果。由於孤立的奈米結構相較於入射光點極小(約1/10)，且不同旋性分子造成的吸收(消光)譜移動極小(約10奈米)，精密定位及抑制熱飄移成為必要。我們擬購置一電控平台，進行回授定位，並購置一低溫恆溫器，期能大幅改良實驗的穩定性。此外，我們亦將發展全新的光譜-色度座標轉換法，優化照射光源使色空間座標之位移最大化，藉以克服譜飄並提升解析精度。上述目標若能達成，將對科學與產業做出貢獻，特別是生物標記、藥/毒物鑑定、食安衛生及環境控制等應用。 ;Sculpting light at nanoscale signifies a substantial step towards comprehensive manipulation of the interaction between photons and molecules. Since plasmon is nearly diffraction unlimited, light can be confined within nano-scale which makes the manipulation of scalar quantities such as wavelength, intensity, and phase easily be achieved. However, being capable of manipulating the polarization state at nanoscale at one’s desire is still challenging. This has been widely recognized as the last mile towards comprehensively control the interactions between photons and molecules, just like the famous remark made by Michael Faraday more than a hundred years ago: “Polarised light is the most subtle and delicate investigator of molecular condition.” Following the results obtained in the first year, in this 2-year-project, we plan to manipulate the polarization state and study the superchiral phenomenon at nanoscale, aiming at facilitating chirality recognition and enantiomer separation. The main methodologies employed in this project include: 1. The fabrication of plasmonic dimer, trimer, or oligomers; 2. Superresolved four wave mixing light generation; 3. Conical refraction based polarimetry; 4. Generalized multiparticle Mie (GMM) simulation; and 5. Waveguide based opto-fluidic technology. So far, preliminary results are obtained both theoretically and experimentally. We will then integrate functionality such as particle transportation by waveguide along with the nanoparticles to achieve chiral recognition and enantiomer separation simultaneously. Since the isolated nanostructure is much smaller than the laser spot (~1/10) and the shift of the absorption/scattering spectrum for molecules with opposite chirality is very small (~10 nm), we request a motor stage and a cryostat to improve the power stability and mitigate deadly thermal drift. It is hoped that with the requested instruments, the resolution and sensitivity can be largely improved. Besides, we will develop a brand-new algorithm based on the conversion between the measured spectrum and CIE 1931 color coordinates. The guidelines about synthesizing the optimal light source to maximize the coordinate shift for oppositely handed enantiomers will be yielded. This will enable one to distinguish chirality directly on the map. If the abovementioned targets are successfully achieved, the results will benefit to the scientific society and industry, in particular for the application in the field of bio-labeling, drug/toxicant identification, food safety, and environment monitoring. |
