An ultra-wide bandwidth single-polarization single-mode hollow-core anti-resonant fiber based on epsilon-near-zero material coatings

Abstract The polarization characteristics of optical fibers are of crucial importance in optical fiber communication and sensing applications. Single-polarization single-mode (SPSM) fibers can ensure a stable polarization state and high-quality signal transmission. Hollow-core anti-resonant fibers (HC-ARFs) have advantages such as a simple structure and wide bandwidth. However, current SPSM HC-ARFs have limitations in bandwidth and structural complexity. In this paper, a method to enhance the SPSM characteristics of a simple-structured HC-ARF is proposed by introducing epsilon-near-zero (ENZ) material coatings into some of its air holes. The full-vector finite element method is employed to investigate the influence of the fiber structural parameters and the thickness of the coatings on the SPSM bandwidth. The key factors affecting the SPSM bandwidth are explored, and the relevant parameters are optimized based on the corresponding analysis. The results demonstrate that a wide SPSM bandwidth of 716 nm can be achieved for minimum loss difference (MLD) ≥ 40 dB m −1 and 431 nm for the condition of MLD ≥ 100 dB m −1 , indicating that the method can significantly improve the SPSM bandwidth of the HC-ARF. To the best of our knowledge, this is the largest SPSM bandwidth that can be achieved at present. The research provides a novel design and optimization method for SPSM HC-ARFs, which will promote its application in related fields.