The capacity of optical communication channels can be increased by space division multiplexing in structured optical fibers. Radial core optical fibers allows for the propagation of twisted light–eigenmodes of orbital angular momentum, which have attracted considerable attention for high-dimensional quantum information. Here we study the generation of entangled photons that are tailor-made for coupling into ring core optical fibers. We show that the coupling of photon pairs produced by parametric down-conversion can be increased by close to a factor of three by pumping the non-linear crystal with a perfect vortex mode with orbital angular momentum ℓ, rather than a gaussian mode. Moreover, the two-photon orbital angular momentum spectrum has a nearly constant shape. This provides an interesting scenario for quantum state engineering, as pumping the crystal with a superposition of perfect vortex modes can be used in conjunction with the mode filtering properties of the ring core fiber to produce simple and interesting quantum states.

通过在结构化光纤中进行空分复用，可以增加光通信信道的容量。径向纤芯光纤允许轨道角动量的扭曲光本征模式的传播，这在高维量子信息方面引起了相当大的关注。在这里，我们研究了为耦合到环芯光纤中而定制的纠缠光子的产生。我们表明，通过以具有轨道角动量的完美涡旋模式泵浦非线性晶体，参数下转换产生的光子对的耦合可以增加接近三倍ℓ，而不是高斯模式。此外，双光子轨道角动量谱具有几乎恒定的形状。这为量子态工程提供了一个有趣的场景，因为可以将具有完美涡旋模式叠加的晶体与环芯光纤的模式过滤特性结合使用，以产生简单而有趣的量子态。