Vortex beams carrying orbital angular momentum have attracted a great deal of attention over the past few years. An integrated vortex beam generator with high efficiency is desirable for wide-ranging applications. Here we demonstrate a highly efficient silicon photonic integrated vortex beam generator based on superposed holographic fork gratings. A metal mirror is used to enhance emission efficiency by reflecting the power leaking down to the substrate back to air. Experimental characterization confirms that the emission efficiency of the generator increases by ${\sim} 5\,{\rm dB}$. Moreover, the present device shows preferable features of broadband, polarization diversity, and compact footprint.

中文翻译：

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电信C频段内的紧凑型高效四模涡旋光束发生器

在过去的几年中，带有轨道角动量的涡旋光束引起了极大的关注。具有高效率的集成涡旋光束发生器是广泛应用的理想选择。在这里，我们演示了一种基于叠加全息叉状光栅的高效硅光子集成涡流发生器。金属镜用于通过将泄漏到基板的功率反射回空气来提高发射效率。实验特性证实，发生器的发射效率提高了$ {\ sim} 5 \，{\ rm dB} $。而且，本设备显示了宽带，极化分集和紧凑的足迹的优选特征。