Diniz K, Dutra R S, Pires L B, Viana N B, Nussenzveig H M, Maia Neto P A
Opt Express. 2019 Mar 4;27(5):5905-5917. doi: 10.1364/OE.27.005905.
We show that the optical force field in optical tweezers with elliptically polarized beams has the opposite handedness for a wide range of particle sizes and for the most common configurations. Our method is based on the direct observation of the particle equilibrium position under the effect of a transverse Stokes drag force, and its rotation around the optical axis by the mechanical effect of the optical torque. We find overall agreement with theory, with no fitting, provided that astigmatism, which is characterized separately, is included in the theoretical description. Our work opens the way for characterization of the trapping parameters, such as the microsphere complex refractive index and the astigmatism of the optical system, from measurements of the microsphere rotation angle.
我们表明，在具有椭圆偏振光束的光镊中，对于广泛的粒子尺寸范围和最常见的配置，光力场具有相反的手性。我们的方法基于对横向斯托克斯拖曳力作用下粒子平衡位置的直接观测，以及通过光扭矩的机械效应使其绕光轴旋转。我们发现，只要在理论描述中包含单独表征的像散，就能在无需拟合的情况下与理论总体一致。我们的工作为从微球旋转角度的测量中表征捕获参数（如微球复折射率和光学系统的像散）开辟了道路。
