Orbital motion of optically trapped particles in Laguerre-Gaussian beams.
Orbital motion of optically trapped particles in Laguerre-Gaussian beams.
复制标题
DOI：
10.1364/josaa.27.002061
复制
发表时间：
2010-09
期刊：
影响因子：
--
通讯作者：
S. Simpson;S. Hanna
中科院分区：
文献类型：
--
作者：
S. Simpson;S. Hanna
对瑞利和米氏两种非傍轴拉盖尔-高斯光束的离轴囚禁进行了理论研究。众所周知，作用在粒子上的力可以分为与强度梯度成比例的项和表示散射力的项。后一项可以进一步细分为耗散辐射力和依赖于电场梯度的项。对于拉盖尔-高斯光束中的瑞利粒子，场梯度项恰好贡献了散射力的一半。这可以与平面波相比，在平面波中，它的贡献为零。半径从0.1到0.5微米和折射率的范围内的球体的离轴捕获位置的数值计算在米氏制度，使用共轭梯度法。对于具有不同轨道角动量和偏振状态的光束，给出了处于捕获位置的粒子的方位力和轨道扭矩。的“自旋”扭矩的组件，通过粒子的中心，也计算吸收粒子在米氏政权。
A theoretical examination of off-axial trapping in non-paraxial Laguerre-Gaussian beams is presented for both the Rayleigh and Mie regimes. It is well known that the force acting on a particle may be divided into a term proportional to the intensity gradient and another representing the scattering force. The latter term may be further sub-divided into a dissipative radiation force and a term dependent on the electric field gradient. For Rayleigh particles in Laguerre-Gaussian beams, it is shown that the field gradient term contributes exactly half of the scattering force. This may be compared with a plane wave, in which it makes zero contribution. The off-axis trapping positions for spheres with radii varying from 0.1 to 0.5 mum and a range of refractive indices are calculated numerically in the Mie regime, using a conjugate gradient approach. Azimuthal forces and orbital torques are presented for particles in their trapping positions, for beams with different orbital angular momentum and polarization states. The components of a "spin" torque, acting through the center of the particle, are also computed for absorbing particles in the Mie regime.