離焦探測光束式高解析範圍光子力顯微鏡之架設與應用

Abstract

光子力顯微術為結合雷射鑷夾與四象限光偵測器的單一微粒子追蹤技術，其原理為利用四象限光偵測器偵測被微小粒子散射之雷射光而可偵測微小粒子之位移達奈米級解析度。但由於微粒子的大小對於散射光分布的影響甚鉅，因而影響四象限光偵測器對散射光之響應。所以我們提出引入另一道雷射光作為探測光束，針對不同大小的微粒子調整探測光束的聚焦位置，得到最佳的四象限光偵測器對散射光之響應。在本論文中，我們將探測光束聚焦於微粒子前，並利用微粒子的微透鏡效應使得四象限光偵測器可以獲得最佳的響應。我們利用模擬及實驗的方式，觀察不同的探測光束聚焦位置所產生的散射光圖樣，以及四象限光偵測器對散射光光斑的響應，並提出最佳的離焦探測光束架設方式。我們分別針對直徑為1、3、6 □m的塑膠小珠進行模擬及實驗，並且得到探測光束最佳的聚焦位置為塑膠小珠中心前2/3倍直徑的位置。此外，我們驗證了新架設的離焦探測光束式光子力顯微鏡具有小於10 nm的空間解析度。且我們利用這套系統校正了雷射鑷夾的光彈簧係數並驗證了利用光彈簧係數法量測生物力彈簧的可行性。

Photonic Force Microscopy is a single particle tracking technique which operates by combining an optical tweezers and a quadrant photo detector (QPD). The movement of the micro-particle is tracked by using a QPD to detect the scattering light from the particle, which is illuminated by the laser beam. The spatial resolution of this particle-tracking technique can reach under a few nanometers. Nevertheless, the size of micro-particle influences the scattering light a lot and consequently, influence the response of the QPD to the scattering light. . Therefore, we propose to import another laser beam to be a probing beam. By adjusting the focus of the probing beam according to different sizes of particle, one can always obtain the best response of the QPD to the scattering light. In this thesis, we focused the probing beam in front of micro particle, and let the QPD could have the best response by the micro lens effect of the micro particle. We used optical-simulation program and an experiment to observe the scattering light under different probing beam focusing position, and we also observe the response of the QPD to these different scattering patterns. We performed the simulation and experiments of the signal response upon three kinds of trapped polystyrene beads whose size are 1-□m, 3-□m, and 6-□m-in-diameter, respectively. It also obtained that the optimized distance between the probing laser focus and a trapped bead is one third of the diameter of the bead in front of the center of the bead. Besides, we attained that the spatial resolution of our Probing Beam Type Photonic Force Microscope (PBPFM) to track a particle is less than 10 nm. At last, the stiffness of our optical tweezers with our PBPFM is calibrated and the possibility to measure the adhesive stiffness of biological samples by stiffness method is also confirmed. At last, the stiffness of our optical tweezers with our PBPFM is calibrated and the possibility to measure the adhesive stiffness of biological samples by stiffness method is also confirmed.