Characterizing hollow-core fiber surface roughness with large dynamic range and picometer-resolution profilometry

We report on the design and characterization of a picometer-resolution optical profilometer with a large dynamic range for assessing the surface roughness of the elements forming the microstructure of hollow-core photonic crystal fibers (HCPCFs). The characterization of the device allowed us to demonstrate a sensitivity of 2pm/Hz and, remarkably, a dynamic range of 1 cm. In addition, we were able to demonstrate the applicability of the profilometer in measuring the surface roughness levels inside different HCPCF designs. Our results validate the profilometer operation and reveal this device as a powerful tool to be integrated into HCPCF development chains.