Department of Chemistry, PTCL, University of Oxford, South Parks Road, Oxford, OX1 3QZ, UK.
Phys Chem Chem Phys. 2012 Dec 5;14(45):15826-31. doi: 10.1039/c2cp42925j. Epub 2012 Oct 23.
In this paper we explore the trapping of aerosol droplets using an annular beam, formed by blocking the central portion of a Gaussian beam, and quantify the improvements over conventional Gaussian beam traps. Recent work on the modelling of single aerosol dynamics within an optical tweezer trap [Burnham et al., Journal of the Optical Society of America B, 2011, 28, 2856-2864] has indicated that the use of annular beams can allow smaller droplets to be trapped, which we experimentally verify. We also demonstrate that annular beams allow droplets to be trapped at higher powers, and with reduced axial displacement with increasing power, than Gaussian beams. We confirm these results, due to a reduction in the axial scattering forces, using this theoretical model. Finally back focal plane interferometry is used to determine the axial and lateral trap stiffnesses for a series of droplets, showing a significant increase in the axial : lateral trap stiffness ratio from 0.79 ± 0.04 to 1.15 ± 0.04 when an annular beam is used.
在本文中，我们探索了使用环形光束捕获气溶胶液滴的方法，该环形光束是通过阻挡高斯光束的中心部分形成的，并定量分析了其相对于传统高斯光束陷阱的改进。最近关于光学镊子陷阱中单气溶胶动力学建模的工作[Burnham 等人，美国光学学会杂志 B，2011，28，2856-2864]表明，使用环形光束可以捕获更小的液滴，我们通过实验验证了这一点。我们还证明，与高斯光束相比，环形光束可以在更高的功率下捕获液滴，并且随着功率的增加轴向位移减小。我们使用该理论模型证实了这些结果，这是由于轴向散射力的减小。最后，使用背焦面干涉法确定了一系列液滴的轴向和横向陷阱刚度，当使用环形光束时，轴向：横向陷阱刚度比从 0.79±0.04 显著增加到 1.15±0.04。
