Etching of UHNA3 fiber with hydrofluoric acid

The dataset shows the etching depth of the UHNA3 fiber as a function of time. The region surrounding the core (with an unknown dopant) etches faster than the cladding but more slowly than the core. The etching liquid consisted of a 1:1 mixture of 51% hydrofluoric acid (HF) and distilled water. The etching depth was determined based on the shift of interference fringes measured using white-light interference microscopy, with a glass plate in contact with the fiber end face. An example image and the corresponding fringe shift are included in the dataset file. The measured etching rates are approximately: a) 1.5 nm/s (in addition to the cladding etching rate) for the region surrounding the core, with a diameter of approximately 15 µm, b) 2.6 nm/s (in addition to the cladding etching rate) for the core. The cladding is also etched, however, its etching rate was not determined in this experiment because bare fibers were used.