Measuring the complete force field of an optical trap
Measuring the complete force field of an optical trap
复制标题
DOI：
10.1364/ol.36.001260
复制
发表时间：
2011-04-01
期刊：
影响因子：
3.6
通讯作者：
Grill, Stephan W.
中科院分区：
文献类型：
--
作者：
Jahnel, Marcus;Behrndt, Martin;Grill, Stephan W.
使用光学陷阱在分子水平上测量或施加力需要对陷阱力场有精确的了解。在接近陷阱中心的位置，这个场通常被近似为被捕获微球的位移的线性。然而，在低激光强度下需要高力的应用可以探测超出线性区域的光-微球相互作用。在此，我们利用背焦平面光探测的双光束光陷装置，测量了二维光陷的完全非线性作用力和位移响应。我们观察到陷阱在依赖于微球大小的线性区域之外有很大的刚性，这与Mie理论的计算一致。令人惊讶的是，我们发现力的线性检测范围远远超过了位移的检测范围。我们的方法允许对光学陷阱进行完全校准。(C)2011年美国光学学会
The use of optical traps to measure or apply forces on the molecular level requires a precise knowledge of the trapping force field. Close to the trap center, this field is typically approximated as linear in the displacement of the trapped microsphere. However, applications demanding high forces at low laser intensities can probe the light-microsphere interaction beyond the linear regime. Here, we measured the full nonlinear force and displacement response of an optical trap in two dimensions using a dual-beam optical trap setup with back-focal-plane photodetection. We observed a substantial stiffening of the trap beyond the linear regime that depends on microsphere size, in agreement with Mie theory calculations. Surprisingly, we found that the linear detection range for forces exceeds the one for displacement by far. Our approach allows for a complete calibration of an optical trap. (C) 2011 Optical Society of America