Gilded Hollow-Core Fibers for Sensing and Endoscopy

Hollow core fibers that guide waves in a void offer numerous applied possibilities due to their extended light-matter interaction length and strong optical confinement. By adding functional materials to the inner capillary, one can customize the fiber's optical characteristics, transforming it into a practical device. Here we demonstrate an anti-resonant hollow-core fiber, decorated with gold nanoparticles. Particles with an average size of ~20 nm in size provide ~45% surface coverage over tens of centimeters inside the capillary. Since the fundamental mode and the gold layer have a moderately low overlap, the fiber retains its high transmission capabilities. Nevertheless, significant heating of a liquid, filling the fiber capillary, occurs throughout the structure, as detected and measured with a thermal camera. Our experiments also revealed that at moderate laser intensities, the liquid inside the fiber starts to boil, disrupting the optical guidance. This gilded hollow core fiber, with its high thermo-optical responsiveness, is promising as an effective optically driven catalytic reactor in scenarios requiring small reaction volumes or remote process control.