近日，苏州大学的Yahong Chen及其研究小组与东芬兰大学的Andreas Norrman等人合作并取得一项新进展。经过不懈努力，他们揭示紧聚焦双色光学利萨如光束中自旋角动量密度和自旋矢量的方向差异性。相关研究成果已于2024年4月2日在国际知名学术期刊《物理评论A》上发表。

在这项工作中，研究人员考虑紧密聚焦的双色利萨如光束，并表明自旋角动量密度矢量和自旋矢量在这种三维光场中可能指向明显不同的方向，在某些情况下几乎是正交的，因此通常提供了关于光自旋的不同信息。

据悉，对于单色光场，其偏振椭圆在某一点必然位于固定平面内，自旋角动量密度矢量与反映光场偏振特性的自旋矢量是平行的。相反，多色光的电场通常可以向三个方向演化，使得它们的平均强度在参照系的任何方向上都是非零的。因此，这两个向量不再是平行的。

附：英文原文

Title: Directional difference of the spin angular-momentum density and spin vectors in tightly focused bichromatic optical Lissajous beams

Author: Xinlu Zhu, Xiangyun Li, Zhen Dong, Fei Wang, Lin Liu, Andreas Norrman, Tero Setl, Yangjian Cai, Yahong Chen

Issue&Volume: 2024/04/02

Abstract: The spin angular-momentum density vector and the so-called spin vector reflecting the polarization properties of a light field are parallel for a monochromatic light field whose polarization ellipse at a point necessarily lies in a fixed plane. In contrast, the electric field of polychromatic light may, in general, evolve in three directions such that the average intensity in all of them is nonzero for any orientation of the reference frame. Consequently, the two vectors are no longer necessarily parallel. In this work we consider tightly focused bichromatic Lissajous beams and show that the spin angular-momentum density vector and the spin vector in such three-dimensional light fields may point in markedly different directions, almost orthogonal in some cases, and thus generally provide different information on the spin of light.

DOI: 10.1103/PhysRevA.109.043503

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.109.043503