Anti-Resonant Fiber with Large Mode Area and Ultra-High HOMER for Near-Infrared High-Power Laser

A novel anti-resonant hollow-core fiber (AR-HCF) is proposed. The fiber uses cross-nested circular cladding tubes including single-nested and non-nested tubes in the near-infrared spectral region of 1.3–1.7 μm. All the anti-resonant tubes are used to minimize the confinement loss (CL) of the LP01 core mode. The non-nested tubes are also employed to achieve single-mode performance through strong mode coupling between the cladding mode and the LP11 core mode. The impact of the structural parameters on the CL of the modes is analyzed by using the finite element method (FEM). Optimization results indicate that the CLs of the LP01 mode and the LP11 mode are 0.18 dB/km and 5.88 × 103 dB/km at 1.55 μm. Consequently, the higher-order mode extinction ratio (HOMER) achieves 3.27 × 104. Additionally, the mode field area of the fiber exceeds 4720 μm2 and the corresponding mode field diameter of the LP01 mode is more than 77 μm across the spectral region of 1.3–1.7 μm. In the practical applications, the fabrication tolerance is analyzed. The collapse of anti-resonant tubes within 0–2 μm and positional offsets between 0° and 4° both have minimal impact on fiber performance, thereby ensuring the stability of the system. Compared with other reported fibers, the proposed fiber demonstrates superior performance.