Nested capillary anti-resonant silica fiber with mid-infrared transmission and low bending sensitivity at 4000  nm

Klimczak M., Dobrakowski D., Ghosh A.N., Stępniewski G., Pysz D., Huss G., Sylvestre T., Buczyński R.

Optics Letters

44(17), 2019, 4395-4398, 10.1364/OL.44.004395

We report a silica glass nested capillary anti-resonant nodeless fiber with transmission and low bending sensitivity in the mid-infrared around 4000 nm. The fiber is characterized in terms of transmission over 1700–4200 nm wavelengths, revealing a mid-infrared 3500–4200 nm transmission window, clearly observable for a 12 m long fiber. Bending loss around 4000 nm is 0.5 dB/m measured over three full turns with 40 mm radius, going up to 5 dB/m for full turns with 15 mm radius. Our results provide experimental evidence of hollow-core silica fibers in which nested, anti-resonant capillaries provide high bend resistance in the mid-infrared. This is obtained for a fiber with a large core diameter of over 60 μm relative to around 30 μm capillaries in the cladding, which motivates its application in gas fiber lasers or fiber-based mid-infrared spectroscopy of COx or NxO analytes.