晶片系統中用於操控微米及奈米粒子之近場光鑷夾設計

Abstract

光學作用力使得微小粒子之非接觸式及非破壞性操控成為可能，而此特性是任何機械式鑷夾所達不到的。近年來應用消逝波產生作用力用於積體化光學粒子捕捉已經開啟操控粒子於晶片實驗室系統中的可能。由於近場中高度侷域化的場分布，次微米或甚至奈米尺度的粒子皆可被精確的操控，而此精確度更甚於傳統工具的使用。然而消逝場強總是比較弱，因此入射光能量必須提高才成產生足夠的光學作用力。以微共振腔或表面電漿結構中的共振模態增進光學作用力並降低耗能的技術已是許多研究的關注對象。再者，此共振特性將提供免標定偵測奈米粒子或分子的可能性並伴隨高偵測率。如此多功能並且相容於平行操控的元件將是晶片實驗室發展用於生化應用中的關鍵要素。 此論文將針對發展具有多功能之晶片上之光學操控系統，包含粒子捕捉、傳遞、偵測、與環境折射率感測。首先藉由光子晶體波導的慢光效應設計，我們得以發展非常有效率的粒子傳遞系統。為增進近場光學操控的控制能力，我們利用寬度漸變的光子晶體波導設計提出一個稱為可控制式傳遞的全新功能。之後為追求粒子捕捉系統的緊實度，我們結合表面電將結構於光波導上。然而為發展既緊實又有效率的粒子捕捉系統，同時具有粒子偵測與環境折射率感測的功能，我們轉為設計一維的光子晶體共振腔。首先我們提出具腰部設計的奈米樑光子晶體共振腔，此腰部設計可容納各種尺寸的微小粒子，並可以達到單位為奈牛頓等級的捕捉力紀錄。最後藉由表面共振模態於奈米魚骨共振腔的設計，我們進一步將此記錄推至數十奈牛頓。同時這些結構對於粒子偵測以及折射率感測的能力皆相當顯著。我們期待這些於晶片上的粒子操控方式將可以被廣泛的應用於奈米科技以及環境與生命科學之中。

Optical force enables the contactless and nondestructive manipulation of tiny fragile objects which is unachievable by any mechanical tweezers. Recent research on integrated optical trapping using the forces induced by evanescent fields has opened up new opportunities for the manipulation in lab-on-a-chip systems. Due to the highly localized field distribution in near field region, particles of sub-micrometer and even nanometer size can be manipulated with precision higher than most conventional tools. However the evanescent field is always weak and therefore the input power must be high to generate force of sufficient strength. Considerable interest has emerged for the use of resonant mode in either optical microcavity or plasmonic structures as ways to enhance optical forces and lower power consumption. Moreover, the resonant characteristic will provide possibility for label-free detection of nanoparticles and molecules with high sensitivity. Such a multiple functional device, which is compatible with parallel manipulation, will be a key component in lab on chip development for bio-chemistry applications. This dissertation focuses right on demonstration of on-chip optical manipulation system with multiple functionalities, including trapping, transportation, detection, and sensing. By design of photonic crystal waveguide, we demonstrate a particle transportation system which is very efficient due to the implementation of slow light effect. For increasing the controllability of near-field optical manipulation, a brand new functionality called controllable transportation is proposed using tapered photonic crystal waveguide. For pursuing compactness of a trapping system we also integrate plasmonic structure on optical waveguide. To develop a compact and efficient trapping system with detection and sensing functionality at the same time, we turn to design one-dimensional photonic crystal cavity. We first propose a nanobeam photonic crystal cavity with waist structure which is accessible for particle of various sizes. This design reaches a trapping force record at nano-Newton level. At the end of this work we further push the record to the level of a few tens of nano-Newton by surface-like resonant mode of nano-fishbone photonic crystal cavity. Meanwhile its abilities in particle detection and surrounding medium sensing are quite remarkable. We anticipate these on-chip particle manipulation approaches we introduce could lead to various applications in nanotechnology and the environmental and life sciences.