Pal Sushanta Kumar, Rusch Leslie A
Department of Electrical and Computer Engineering, Centre for Optics, Photonics, and Lasers (COPL), Université Laval, Québec, QC, G1V 0A6, Canada.
Sci Rep. 2024 Jun 12;14(1):13565. doi: 10.1038/s41598-024-64392-y.
The scientific community studies tight focusing of radially and azimuthally-polarized vector beams as it is a versatile solution for many applications. We offer a new method to produce tight focusing that ensures a more uniform intensity profile in multiple dimensions, providing a more versatile and stable solution. We manipulate the polarization of the radially and azimuthally polarized vector beams to find an optimal operating point. We examine in detail optical fields whose polarization states lie on the equator of the relevant Poincaré spheres namely, the fundamental Poincaré sphere, the hybrid order Poincaré sphere (HyOPS), and the higher order Poincaré sphere. We find via simulation that the fields falling on these equators have focal plane intensity distributions characterized by a single rotation parameter determining the individual state of polarization. The strengths of the component field distributions vary with and can be tuned to achieve equal strengths of longitudinal (z) and transverse (x and y) components at the focal plane. Without control of this parameter (e.g., using in radially and in azimuthally-polarized vector beams) intensity in x and y components are at 20% of the z component. In our solution with , all components are at 80% of the maximum possible intensity of z. In examining the impact of on a tightly focused beam, we also found that a helicity inversion of HyOPS beams causes a rotation of 180 degree in the axial intensity distribution.
科学界对径向和角向偏振矢量光束的紧聚焦进行了研究,因为它是许多应用的通用解决方案。我们提供了一种产生紧聚焦的新方法,该方法可确保在多个维度上具有更均匀的强度分布,从而提供更通用、更稳定的解决方案。我们操纵径向和角向偏振矢量光束的偏振,以找到最佳工作点。我们详细研究了偏振态位于相关庞加莱球赤道上的光场,即基本庞加莱球、混合阶庞加莱球(HyOPS)和高阶庞加莱球。通过模拟我们发现,落在这些赤道上的光场在焦平面上的强度分布由一个单一的旋转参数表征,该参数决定了各自的偏振状态。分量场分布的强度随该参数变化,并且可以进行调整,以在焦平面上实现纵向(z)和横向(x和y)分量的强度相等。如果不控制这个参数(例如,在径向偏振矢量光束中使用该参数,在角向偏振矢量光束中使用该参数),x和y分量的强度仅为z分量的20%。在我们的解决方案中,所有分量的强度均为z分量最大可能强度的80%。在研究该参数对紧聚焦光束的影响时,我们还发现HyOPS光束的螺旋度反转会导致轴向强度分布旋转180度。