Efficient light coupling into the fiber waveguides is important in numerous applications, while the low in‐coupling coefficients of commercially available step‐index fibers significantly narrow their application domains. It is recently introduced that well‐defined periodic nanostructures, such as annulus gratings, allow to substantially boost in‐coupling coefficients. In this study, the genetic algorithm is applied for the optimization of trapezoidal polymer gratings. The experimental data showcase multiply enhanced light coupling at preselected incident angles with respect to a bare fiber. As a breakthrough result, the development of an axial‐asymmetric four‐sector grating, reaching the percentage level of light coupling efficiency in a broad angular range from 0 to 70 that outperforms axial‐symmetric gratings by about order of magnitude. Further, the high average light coupling efficiency is verified in the finite angular intervals at multiple wavelengths of 650, 1000, and 1550 nm. This solution highlights the enhancement of algorithm‐designed structures axially‐asymmetric systems for fiber‐based highly efficient light collections, that will further benefit extensive applications such as wide‐field endoscopies.

中文翻译：

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由轴向不对称四扇区纳米结构提供支持的光纤尖端，用于广角光耦合


在许多应用中，光耦合到光纤波导中非常重要，而市售阶跃折射率光纤的低耦合系数大大缩小了其应用领域。最近介绍，定义明确的周期性纳米结构，如环形光栅，可以大大提高耦合系数。本研究将遗传算法应用于梯形聚合物光栅的优化。实验数据显示了相对于裸光纤在预选入射角处的增强光耦合的倍增。作为一个突破性的结果，轴向不对称四扇形光栅的开发，在 0 ${}^{\circ }$ 到 70 的宽角度范围内达到光耦合效率的百分比水平 ${}^{\circ }$ ，其性能比轴对称光栅高出约一个数量级。此外，在 650、1000 和 1550 nm 多个波长的有限角度间隔中验证了较高的平均光耦合效率。该解决方案突出了算法设计结构轴向不对称系统的增强，用于基于光纤的高效光收集，这将进一步使宽视野内窥镜等广泛应用受益。