Low-loss tellurite anti-resonant hollow-core fiber with nested capillaries

We report a tellurite anti-resonant hollow-core fiber (AR-HCF) with a nested capillary structure. To the best of our knowledge, this fiber, comprising five sets of nested double-layer capillaries around the air core, is the first nested AR-HCF fabricated using infrared glass. Benefiting from the enhanced light confinement capability of the nested capillary design, the fabricated fiber achieves a low transmission loss of 0.15 ± 0.04 dB/m at a single wavelength of 4.65 μm measured by cutting from 3 m to 1 m. A 0.8-m-long nested tellurite AR-HCF delivers near-diffraction-limited laser output, with a beam quality (M²) of 1.07. Numerical simulations confirm that the nested structure reduces confinement loss by approximately two orders of magnitude compared to the single-layer capillary configuration. With further optimization of the fabrication process, the nested tellurite AR-HCF is expected to achieve lower losses, thereby demonstrating substantial potential for applications in mid-infrared (3-10 μm) laser transmission systems.