Accurate Estimation of Refractive Indices of Organic Microparticles in Dual-Beam Optical Trap
Accurate Estimation of Refractive Indices of Organic Microparticles in Dual-Beam Optical Trap
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DOI：
10.1109/embc44109.2020.9176338
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发表时间：
2020-07
期刊：
影响因子：
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通讯作者：
Aotuo Dong;M. Islam;S. Albin;M. Deo
中科院分区：
文献类型：
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作者：
Aotuo Dong;M. Islam;S. Albin;M. Deo
折射率是表征粒子光学性质的重要参数。在双光束光阱中，使用两个反向传播的激光束来捕获悬浮在水介质中的微粒。当光线从一种较低RI的介质（例如水性悬浮介质）传递到另一种较高RI的介质（例如悬浮颗粒）时，其动量发生变化，从而在颗粒表面上施加成比例的捕获力。因此，需要准确了解颗粒和周围介质的RI来确定光阱中颗粒的行为。微尺寸珠粒的RI可以使用传统的光学方法如吸收显微镜进行实验测量。我们开发了一种替代的理论方法来估计的RI的基础上非接触式光学捕获的实验结果被困粒子。在我们的研究中，一个理论模型制定的基础上，实验测量的最小捕获功率的聚苯乙烯和聚乙烯珠使用双光束的光学设置。模型预测的捕集功率-折射率曲线的趋势与实验测量的结果吻合得很好。我们的技术提供了一种替代方法来确定某种微米颗粒的RI，无论其尺寸或密度如何。我们的方法是特别有利的传统方法来确定RI的生物颗粒表现出显着的变化，基于生理和环境条件。
The Refractive Index (RI) is an important parameter of characterizing optical properties of particles. In a dual-beam optical trap, two counter-propagating laser beams are used to trap micro-particles suspended in an aqueous medium. When a ray of light passes from one medium of lower RI (e.g. aqueous suspension medium) to another medium of higher RI (e.g. suspended particle), its momentum changes which exerts a proportional trapping force on the surface of the particle. Thus, accurate knowledge of RI of the particles and the surrounding medium is needed to determine the behavior of particles in an optical trap. The RI of micro-sized beads can be experimentally measured using traditional optical methods such as absorption microscopy. We developed an alternative theoretical method to estimate the RI of trapped particles based on non-contact optical trapping experimental outcomes. In our study, a theoretical model was formulated based on the experimentally measured minimum trapping powers for polystyrene and polyethylene beads using a dual-beam optical setup. The tendencies of trapping power-RI curves predicted by our model agreed very well with those measured experimentally. Our technique provides an alternative approach to determining the RI of a certain micro-size particle regardless of its size or density. Our method is especially advantageous over traditional methods to determine RI of biological particles which exhibit significant variations based on physiological and environmental conditions.