AUTHORS:

Gronowicz P., Perehiniec P., Pałka K., Filipkowski A., Buczyński R., Nikodem M.

ABSTRACT:

This work presents the proof-of-concept for a highly miniaturized gas-sensing probe based on an antiresonant hollow-core fiber (ARHCF) operating in a reflective configuration. The probe uses an internal gold-coated fiber mirror to reflect light back through the core. Because the fiber end is blocked by the mirror, gas enters the hollow core through multiple side openings milled near the probe tip. To achieve the required structural modifications without collapsing the delicate thin-walled cladding, both focused ion beam (FIB) micromilling and ultraviolet femtosecond laser processing were successfully employed. The functional relevance of this integrated architecture is verified through methane detection in the mid-infrared region (3.27 µm) using wavelength modulation spectroscopy (WMS). We demonstrate a rapid gas exchange response time of ∼3 s, matching that of an open-ended fiber, and an estimated detection limit of ∼560 ppb. Ultimately, the results establish a robust structural framework for endoscope-like lab-in-fiber systems, paving the way for advanced, ultra-compact gas or optofluidic point-sensors.

Optics and Laser Technology, 2026, vol. 203 part D, art. 116272, doi: 10.1016/j.optlastec.2026.116272