All-fiber delivery of 1.3 kW laser power through a hollow-core anti-resonant fiber with a 14 μm mode field diameter.

Hollow-core anti-resonant fibers (HC-ARFs) provide an attractive platform for high-power laser delivery because most of the optical field propagates in air, enabling high damage thresholds, weak light-silica interaction, and low optical nonlinearity. Here, we demonstrate all-fiber delivery of 1338 W continuous-wave laser power through a 2-m HC-ARF with a 14-µm mode-field diameter and a coupling efficiency of 97.1%. Efficient coupling is achieved by fusion splicing a mode-matched solid-core delivery fiber to the HC-ARF with an anti-reflection-coated end face and optimized offset-arc parameters. The fiber shows negligible bend-induced loss for bend diameters down to 13 cm, supporting compact and flexible deployment. Furthermore, the system enables passive beam cleaning, improving the beam quality factor (M2) from 1.25 to 1.15 via the preferential attenuation of higher-order modes. This compact all-fiber HC-ARF system combines a small mode field, kilowatt-level power density, and near-diffraction-limited beam quality, offering stable and flexible delivery of high-quality beams.