Fiber-optic gas sensor based on gold nanogaps

We fabricated a fiber-optic gas sensor using a D-shaped optical fiber that interacts with the environment via an evanescent field. Gold was first deposited and annealed to form nano-islands, followed by wet etching using hydrofluoric acid. A second gold deposition created nanogaps, enabling gas sensing functionality. An additional round of gold deposition and annealing before etching improved sensitivity. The sensor showed resonance wavelength shifts depending on the gas type, confirming its potential for compact, low-cost, and highly sensitive gas detection using optical fiber platforms.