In this study, a novel freeform surface lens coupler is designed to realize the coupling functions in the hollow‐core photonic crystal fiber (HCPCF) resonator optical gyroscope. One surface of the lens is an ellipsoid. Coupling of the two HCPCF loop's ports can be directly accomplished via reflection on the ellipsoid surface. The other surface of the lens is the Biconic Zernike surface. Transmitting through the above two surfaces, the coupling between the intracavity and extracavity is completed. In this paper, simulations were performed based on two types of HCPCFs, a hollow‐core photonic bandgap fiber of HC19‐1550 and a state‐of‐the‐art nested antiresonant nodeless fiber. The volume of the lens coupler is calculated to be approximately 4 × 2 × 4 mm3. The simulation results show that the intracavity coupling loss can be as low as 0.011 dB, and the coupling loss between the intracavity and extracavity can be as low as 0.4 dB. Compared with the traditional fusion scheme between hollow‐core fiber and polarization‐maintaining fiber, the freeform surface lens coupler in this paper can achieve lower coupling loss and higher resonance fineness. Compared with other spatial coupling schemes, it has lower coupling loss and fewer coupling components.

中文翻译：

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空心光子晶体光纤谐振光学陀螺自由曲面透镜耦合器的设计与分析

在这项研究中，设计了一种新型自由曲面透镜耦合器来实现空心光子晶体光纤（HCPCF）谐振器光学陀螺仪中的耦合功能。透镜的一个表面是椭球面。两个 HPCCF 环路端口的耦合可以通过椭球表面的反射直接完成。透镜的另一个表面是双锥泽尼克表面。通过上述两个表面的传输，完成腔内与腔外的耦合。在本文中，基于两种类型的HCPCF进行了模拟：HC19-1550的空芯光子带隙光纤和最先进的嵌套反谐振无节点光纤。透镜耦合器的体积经计算约为4×2×4mm3。仿真结果表明，腔内耦合损耗可低至0.011 dB，腔内外耦合损耗可低至0.4 dB。与传统的空心光纤和保偏光纤熔接方案相比，本文的自由曲面透镜耦合器可以实现更低的耦合损耗和更高的谐振精细度。与其他空间耦合方案相比，它具有更低的耦合损耗和更少的耦合分量。