Low-loss, gap-filling, nested, anti-resonant nodeless fiber in the ultraviolet band.

We propose what we believe to be a novel low-loss, gap-filling, nested, anti-resonant nodeless fiber (GF-NANF) designed for ultraviolet (UV) applications. The GF-NANF achieves loss reduction by integrating nested tubes and gap-filling structures. Our results show that the GF-NANF reduces confinement loss by four orders of magnitude to 2.29 × 10^-5dB/m, and propagation loss by two orders of magnitude to 1.64 × 10^-2dB/m, at 355 nm, when compared to an ARF of the same design that lacks both gap-filling cladding tubes and nested cladding tubes. Additionally, the fiber shows simulated low bending losses of 1.01 × 10^-4dB/m at a 10-cm bending radius and 1.40 × 10^-3dB/m at 5 cm, representing a reduction by approximately three orders of magnitude compared to the NANF without gap-filling tubes. Notably, at a bending radius of 10 cm, the GF-NANF maintains quite low bending losses below 1.2 × 10^-4dB/m across all bending orientations from 0° to 360°, significantly lower than that of structures without gap-filling tubes, exhibiting its suitability for UV optical systems requiring high efficiency and operation flexibility.