Low-loss multi-mode anti-resonant hollow-core fibers

In this work, multi-mode anti-resonant hollow-core fiber (AR-HCF) with 18 fan-shaped resonators is fabricated and characterized. The ratio of core diameter over transmitted wavelengths in the lowest transmission band is up to 85. The measured attenuation at 1 µm wavelength is below 0.1 dB/m and the bend loss below 0.2 dB/m at a bend radius smaller than 8 cm. Modal content of the multi-mode AR-HCF is characterized using the S 2 imaging technique and seven LP-like modes in total are identified using a 23.6 meter fiber length. Multi-mode AR-HCFs for longer wavelengths are fabricated by scaling up the same design, extending the transmission window beyond 4 µm wavelength. Low-loss multi-mode AR-HCF could find applications in the delivery of high-power laser light with a medium beam quality, where higher coupling efficiency and laser damage threshold are expected.