Abstract Photonic Crystal Fiber (PCF), as a novel optical fiber, is widely used in the applications of dispersion control, supercontinuum generation, fiber sensing, etc. However, the numerical aperture (NA) of most PCFs is normally too low to obtain a high coupling efficiency, and the transmitted light is easy to diverge, which limited the applications of PCFs. In recent years, the rapid development of metasurface optics provided an unparalleled platform for improving the optical properties and functionality of the PCFs. Here, we designed two PCF devices integrated with the metalens operating in the telecom region on the basis of numerical simulation, namely PCF divergent metalens (PCF-DM) and PCF focusing metalens (PCF-FM). The simulation results demonstrated that the proposed devices can increase the NA of a PCF from less than 0.1 to 0.65 with coupling efficiencies as high as 90% and 85% through shaping the wave front of the incident light. Meanwhile, it is found that PCF-FM can enhance the focusing capability of a PCF and leads to a focus with a size near the diffraction limit, moreover maintaining a high focusing efficiency. Therefore, we anticipate that the reported novel design would contribute to researches of fiber imaging/sensing, fiber laser, and other PCF-based devices.

中文翻译：

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大数值孔径高效宽带光子晶体光纤元透镜

摘要 光子晶体光纤（PCF）作为一种新型光纤，广泛应用于色散控制、超连续谱产生、光纤传感等领域。耦合效率高，透射光容易发散，限制了PCFs的应用。近年来，超表面光学的快速发展为改善 PCF 的光学性能和功能提供了无与伦比的平台。在这里，我们在数值模拟的基础上设计了两个与电信领域运行的元透镜集成的 PCF 器件，即 PCF 发散元透镜（PCF-DM）和 PCF 聚焦元透镜（PCF-FM）。仿真结果表明，所提出的器件可以将 PCF 的 NA 从小于 0.1 增加到 0。65 通过对入射光的波前进行整形，耦合效率高达 90% 和 85%。同时，发现PCF-FM可以提高PCF的聚焦能力，使焦点尺寸接近衍射极限，并保持较高的聚焦效率。因此，我们预计所报道的新颖设计将有助于光纤成像/传感、光纤激光器和其他基于 PCF 的设备的研究。