基于矩阵光学的光镊设计

Design for Optical Tweezers Based on Matrix Optics

光镊已经成为研究单分子生物物理特性的一个基本工具,因而光镊设计是一个极为重要的课题。光镊捕获光路一般由激光器、扩束系统、光束调控系统、共焦系统、光束耦合系统和大数值孔径的物镜组成,通过保持物镜后瞳充满度来实现光镊稳定性。本文根据几何光学,利用矩阵光学进行光镊捕获光路计算,得到了各个透镜间距、透镜和光束调控系统距离、物镜后瞳处光斑大小与光束调控系统处光斑大小的关系、光束调控系统处光斑大小和入射激光光斑大小的关系。本文计算结果表明光镊横向位置和物镜高度无关,并指出了物镜后瞳位于成像透镜后焦面、光束调控系统位于共焦系统后透镜像方焦面处,才能在光镊阱位纵向操控时保持物镜后瞳充满度不变。本文工作为光镊设计和调整提供了非常简洁而有效的理论指导。

Optical tweezers,or single beam gradient force optical traps,are powerful tools in researching biophysical properties of single molecule.We describe how to build optical tweezers based on matrix optics.The design of optical tweezers consists of laying out a trapping laser,a expand lens,a collimation lens,a light beam controller system,several telescopes,and an inverted microscope with a high numerical aperture objective.The distances between optical elements are calculated by ray optics using matrix optics.The trapping stability is satisfied by maintaining the same degree of overfilling of the microscope entrance aperture.The trapping position has nothing to do with objective height.The formulations provide the basis for theoretical analysis for experimental alignment and adjustment.