Single-mode bend-resistant hollow-core fiber with multi-size anti-resonant elements

• Published in: Infrared physics & technology Vol. 123; p. 104159
• Main Authors: Gu, Shuai, Wang, Xin, Jia, Haoqiang, Xing, Zhen, Lou, Shuqin
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.06.2022
• Subjects: Bending loss; Fiber fabrication; Hollow core fiber; Bending loss; Hollow core fiber; Fiber fabrication
• ISSN: 1350-4495; 1879-0275
• DOI: 10.1016/j.infrared.2022.104159

•A novel hollow-core anti-resonant fiber (HC-ARF) with various-diameter anti-resonant elements (AREs) that can simultaneously provide low bending losses and robust single-mode operation is proposed.•Numerical results prove that it can effectively improve the suppression ability to high order modes (HOMs). Meanwhile, the bending loss is reduced by at least one order of magnitude compared with HC-ARF with uniform AREs.•A single-ring HC-ARF with four kinds of ARE diameters is successfully fabricated and experimentally proved to be single-mode and bend-resistant.•We further proposed a modified nested structure that could achieve a simulated bending loss as low as 0.18 dB/m @1.55 μm under a bending radius of 0.75 cm, which is the lowest bending loss among the reported HC-ARFs under such a tight bending radius as far as we know. A novel single-ring hollow-core anti-resonant fiber (HC-ARF) with multi-size tubular anti-resonant elements (AREs) that can simultaneously provide low bending losses and robust single-mode operation is proposed. Numerical results prove that the introduction of multi-size AREs can effectively improve the suppression ability to high order modes (HOMs). The HOM extinction ratio is twice as high as that of single-ring HC-ARF with uniform AREs. Meanwhile, the bending loss is reduced by at least one order of magnitude due to the suppression of bending-induced loss peaks. A single-ring 7-ARE HC-ARF with four kinds of ARE diameters is successfully fabricated. Experimental results demonstrate that under a tight bending radius of 3.5 cm, the bending loss is as low as 0.37 dB/m @1.65 μm. The measured near-field profile through a 5 m-long fiber proves a robust single-mode performance. In order to further reduce the bending loss, we proposed the modified structure by adopting the nested multi-size AREs, achieving a lower bending loss of 0.18 dB/m @1.55 μm under an extremely tight bending radius of 0.75 cm, which is the lowest bending loss among the reported HC-ARFs under such tight bending radius as far as we know. Meanwhile, single-mode performance can be also improved due to a higher HOM extinction ratio of 938. The proposed fiber has great potential for applications in high-power laser delivery and gas-filled HC-ARF lasers.