Gaussian-beam-like bundles of semi-guided waves propagating in a dielectric slab can excite modes with high-order optical angular momentum supported by a circular fiber. We consider a multimode step-index fiber with a high-index coating, where the waves in the slab are evanescently coupled to the modes of the fiber. Conditions for effective resonant interaction are identified. Based on a hybrid analytical–numerical coupled mode model, our simulations predict that substantial fractions of the input power can be focused into waves with specific orbital angular momentum, of excellent purity, with a clear distinction between degenerate modes with opposite vorticity.

中文翻译：

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具有高阶光学角动量的导波的共振van逝激发

在介电平板中传播的高斯光束状半导波束可以激发具有由圆形光纤支撑的高阶光学角动量的模式。我们考虑了具有高折射率涂层的多模阶跃折射率光纤，其中平板中的波waves逝耦合到光纤的模。确定有效共振相互作用的条件。基于混合分析-数值耦合模式的模型，我们的模拟预测，大部分输入功率可以聚焦到具有特定轨道角动量且纯度极高的波中，并且在具有相反涡度的简并模式之间有明显的区别。