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Antiresonant negative curvature hollow-core optical fibers (NC-HCFs) have proven to have great potential for the delivery of high-energy pulses and for continuous wave Mid-infrared fiber gas laser (FGL) systems. However, following the drawing fiber conditions on the designed fiber geometry, the resulting position of transmission bands of the NC-HCFs needs to be matched to both pumping and lasing wavelengths for the FGL with the particular filled gas. In this work, we investigated experimentally the possibilities of adjusting the transmission bands of a short length of the fabricated NC-HCFs to both UV the Mid-infrared directions that would further enhance their usage in FGL. The investigation was based on two steps. The first step involves fabricating a few fibers from a single preform with different inner geometry dimensions concerning the applied pressure into the preform’s capillaries. This would help to calibrate the correlation of adjusted fibers’ transmission bands to the desired wavelength with respect to the applied pressure while drawing. Increasing the pressure into the capillaries from 300 to 400 mm H2O while maintaining the pressure in the preform core at 30 mm H2O the bands were gradually blue-shifted by ~16.5 % to have about 330 nm shift at the first transmission band. This is attributed to the decrease in core diameter, capillaries gaps, and wall-thickness while increasing the capillaries diameter. The second step involves processing a short length of drawn fibers through local heating and tapering for adjusting their transmission bands' positions using a CO2 laser fusion splicer. Processing the whole length of a short fiber segment ~5 cm shows a complete redshift by ~12.2 % and a blueshift by ~10.2 % after heating and tapering respectively. The first transmission band of the processed fiber was shifted about 200 nm after heating and 122 nm after tapering. The parameters of processing were optimized; thus, no insertion losses were observed. Such results urge us to further develop the mechanism of processing fibers to process long lengths of fibers in the future.
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