Study of the laser polarization dependence upon the trapping force of optical tweezers

• Main Author: 蔡玉堂
• Other Authors: 徐琅
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/89960582414574830540

碩士 === 國立交通大學 === 電子物理系所 === 93 === Optical tweezers has become a useful tool for bio-medical research. Also, as the higher accuracy is required for biological force measurement, a more rigorous model of optical tweezers trapping force is necessary. However, the prediction of recent ray-optics model is not confirmed with our experimental result, that trapping force along with the x-axis is always larger than the one along with the y-axis. Therefore, a more correct model is required to describe this phenomenon. Comparing with the recent ray optics model, in our revise model, we further consider the two different kinds of laser polarizations, a circular polarization and a linear polarization. Therefore, we have to analyze the ratio between transverse electric (TE) model and transverse magnetic (TM) mode. With this consideration, the maximum trapping force along with the x-axis is 15.4% larger than the one along with the y-axis. Also, the optical stiffness along with x-axis is 2.5 % larger than the one along with y-axis. Furthermore, we also measured the optical stiffness of our optical tweezers system, and there is 10% difference between the optical stiffness along the two axes. Additionally, it is also confirmed that the predictions of our model is within the experimental error.