In this paper, we have theoretically studied transformations of higher-order modes and angular momentum of light in the optical snake, a coil resonator composed of two evanescently coupled coils of a multimode fiber. To this end, we have developed a full-vectorial theory of normal modes of coupled parallel multimode fibers that allows for the spin–orbit interaction and goes beyond the limits of weak orthogonality approximation. We have studied the evolution of optical vortices and circularly polarized scalar-approximation fiber modes in a two-coil optical snake. We have shown that this system allows a parametric control over the topological charge of the outcoming optical field, as well as its orbital and spin angular momenta.

中文翻译：

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蛇形光纤谐振腔角动量和模式转换的超高效控制

在本文中，我们从理论上研究了光蛇（由多模光纤的两个渐逝耦合线圈组成的线圈谐振器）中光的高阶模式和角动量的变换。为此，我们开发了耦合平行多模光纤的正常模式的全矢量理论，该理论允许自旋-轨道相互作用并超越弱正交性近似的限制。我们研究了双线圈光蛇中光学涡旋和圆偏振标量近似光纤模式的演变。我们已经证明，该系统允许对输出光场的拓扑电荷及其轨道和自旋角动量进行参数控制。