Zhou Jingwen, Tang Jihong, Yin Yaling, Xia Yong, Yin Jianping
Opt Express. 2024 Feb 12;32(4):5339-5352. doi: 10.1364/OE.516620.
The orbital angular momentum (OAM) of light, possessing an infinite-dimensional degree of freedom, holds significant potential to enhance the capacity of optical communication and information processing in both classical and quantum regimes. Despite various methods developed to accurately measure OAM modes, the probing limit of the highest-order OAM remains an open question. Here, we report an accurate recognition of superhigh-order OAM using a convolutional neural network approach with an improved ResNeXt architecture, based on conjugated interference patterns. A type of hybrid beam carrying double OAM modes is utilized to provide more controllable degrees of freedom for greater recognition of the OAM modes. Our contribution advances the OAM recognition limit from manual counting to machine learning. Results demonstrate that, within our optical system, the maximum recognizable OAM modes exceed l = ±690 with an accuracy surpassing 99.93%, the highest achieved by spatial light modulator to date. Enlarging the active area of the CCD sensor extends the number of recognizable OAM modes to 1300, constrained only by the CCD resolution limit. Additionally, we explore the identification of fractional high-order OAM modes with a resolution of 0.1 from l = ±600.0 to l = ±600.9, achieving a high accuracy of 97.86%.
光的轨道角动量（OAM）具有无限维自由度，在经典和量子领域增强光通信和信息处理能力方面具有巨大潜力。尽管已开发出各种方法来精确测量OAM模式，但最高阶OAM的探测极限仍是一个悬而未决的问题。在此，我们报告基于共轭干涉图样，采用具有改进ResNeXt架构的卷积神经网络方法对超高阶OAM进行精确识别。一种携带双OAM模式的混合光束被用于提供更多可控自由度，以更好地识别OAM模式。我们的贡献将OAM识别极限从人工计数推进到机器学习。结果表明，在我们的光学系统中，最大可识别OAM模式超过l = ±690，精度超过99.93%，这是迄今为止空间光调制器所达到的最高精度。扩大CCD传感器的有效面积将可识别OAM模式数量扩展到1300，仅受CCD分辨率限制。此外，我们探索了从l = ±600.0到l = ±600.9分辨率为0.1的分数高阶OAM模式识别，实现了97.86%的高精度。
