功率谱密度法标定光镊的三维光阱刚度

Calibration of Stiffness of Optical Tweezers in Three Dimensions with Power Spectral Density Method

采用四象限探测器和功率谱密度法，搭建了一套快速标定光镊三维光阱刚度的测量系统．实验中，用四象限探测器记录微粒做受限布朗运动时的位置信息，用功率谱密度法标定光阱刚度，测得了直径0．97μmSiO2小球和直径1μmPMMA小球的光阱刚度与激光功率的关系．结果表明：对于SiO2小球，当激光功率为50～120mw时，光阱刚度与激光功率成正比；对于PMMA小球，当激光功率为80～130mw时，光阱刚度与激光功率成正比．该光镊系统可用于生物、物理等微观领域研究的高准确度测力系统．

An optical tweezers system which can accurately and quickly calibrate the stiffness of optical tweezers in three dimensions was set up combined with quadrant photodiode detector and power spectral density method. The limited Brownian motion of the trapped particle was recorded by a quadrant photodiode detector, and the stiffness of optical tweezers was calibrated by power spectral density method. The relations of the laser power with the stiffness of a 0.97 μm-diameter silica bead and of the 1 μm-diameter PMMA bead were investigated. The results indicate that the stiffness is proportional to the laser power at the range from 50 mW to 120 mW of laser power for a 0. 97 μm-diameter silica bead and at the range from 80 mW to 130 mW for a 1 μm-diameter PMMA bead. This system can be used as a precise force measuring tool for microscopic investigation in biology, physics, etc.