Microscopic Evaluation of Acid-Etched Optical Fibers

Abstract

Optical and scanning electron microscopy were used to examine the changes in the surface morphology of optical fibers as a result of acid etching. The resulting surface modifications are modeled and the resulting structures are considered as alternatives to conventional fibers for chemical sensor development. Hydrofluoric acid (HF) etching has been performed on the tips of flat-end graded index fibers, and spherical-end graded and step index fibers. The acid treatment caused the formation of a coneshaped hollow in the center of graded index fiber tips. This structure provides a surface area enhancement of up t o 5.3-fold over untreated fibers. In addition, this cone-shaped cavity provides a sub-nanoliter reservoir in which reagent can be held at the sensing tip of the fiber. Spherical-end fibers provide sur-2123

Miniature optical fiber current sensor based on a graphene membrane

“…. The sensor was fabricated by etching a single‐mode fiber with HF solution , depositing gold layers, and transferring a CVD‐grown graphene membrane (∼3 layers) .…”

“…Fiber tip fabrication and functionalization : A single‐mode fiber was cut and then immersed into an HF–water solution (∼40%) for 9 min. Because of the different etching speeds of the core area and the cladding area , a hole in the center of the fiber tip was fabricated. The fiber tip was attached to a heating stage, whose temperature was set at 340 K, and a piece of paraffin was put onto the fiber without covering the tip.…”