Antiresonant hollow-core fiber with rapid gas exchange for mid-infrared gas spectroscopy

Abstract Fast, sensitive and selective gas detection is vital for applications ranging from environmental monitoring and industrial process control to medical diagnostics. Optical detection techniques, particularly those operating in the mid-infrared, offer high selectivity and sensitivity but often suffer from complex alignment. This work presents the design, fabrication, and experimental validation of a novel antiresonant hollow-core fiber (ARHCF) with a large core diameter (107 µ m) optimized for rapid mid-infrared gas sensing. The fiber features a simple geometry with 12 thin-walled silica capillaries forming the cladding, ensuring effective single-mode propagation at 3.3 µ m and high flexibility. Experimental characterization confirms broad transmission bands up to 3.4 µ m. When applied to methane detection using a 3.3 µ m interband cascade laser, the system achieved a detection limit of 4 parts per billion with 1 s averaging time. Crucially, the enlarged core drastically reduced gas filling and response time to as low as 2.2 s for a 5.2 m fiber. The proposed large-core ARHCF effectively overcomes the trade off between sensitivity and response speed in hollow-core fiber-based gas sensors.