Spin and orbital angular momenta (AM) of light are well studied for free-space electromagnetic fields, even nonparaxial. One of the important applications of these concepts is the information transfer using AM modes, often via optical fibers and other guiding systems. However, the self-consistent description of the spin and orbital AM of light in optical media (including dispersive and metallic cases) was provided only recently [Bliokh et al., Phys. Rev. Lett. 119, 073901 (2017) [CrossRef] ]. Here we present the first accurate calculations, both analytical and numerical, of the spin and orbital AM, as well as the helicity and other properties, for the full-vector eigenmodes of cylindrical dielectric and metallic (nanowire) waveguides. We find remarkable fundamental relations, such as the quantization of the canonical total AM of cylindrical guided modes in the general nonparaxial case. This quantization, as well as the noninteger values of the spin and orbital AM, are determined by the generalized geometric and dynamical phases in the mode fields. Moreover, we show that the spin AM of metallic-wire modes is determined, in the geometrical-optics approximation, by the transverse spin of surface plasmon polaritons propagating along helical trajectories on the wire surface. Our work provides a solid platform for future studies and applications of the AM and helicity properties of guided optical and plasmonic waves.

中文翻译：

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介电纤维和金属线模的角动量，螺旋度和其他特性

对于自由空间电磁场，甚至是非傍轴电磁场，都对光的自旋和轨道角矩（AM）进行了很好的研究。这些概念的重要应用之一是使用AM模式的信息传输，通常是通过光纤和其他引导系统。但是，仅在最近才提供了光在光学介质（包括色散和金属壳）中的自旋和轨道AM的自洽描述[Bliokh等人。，物理 莱特牧师 119，073901（2017）[交叉引用] ]。在这里，我们介绍了圆柱电介质和金属（纳米线）波导的全矢量本征模的自旋和轨道AM的首次精确计算，包括解析和数值计算，以及螺旋度和其他特性。我们发现了显着的基本关系，例如在一般非傍轴情况下圆柱导模的规范总AM的量化。此量化以及自旋和轨道AM的非整数值由模式字段中的广义几何和动态相位确定。此外，我们表明，在几何光学近似中，金属线模的自旋AM由横向自旋确定线表面上沿螺旋轨迹传播的表面等离激元极化子的数量。我们的工作为未来研究和应用导波和等离激元波的AM和螺旋特性提供了坚实的平台。