Fabrication and Analysis of a Gas Sensor Utilizing a Fabry-Perot Interferometer with Varied Thicknesses of ZIF-8 Coating on End-Faced Single-Mode Optical Fiber

This research investigates the potential of integrating optical fiber and sensitive thin film coating materials to develop diverse chemical sensing platforms. We utilized a layer-by-layer synthesis technique, along with specific pre- post treatment methods, to create highly effective nonporous metal-organic frameworks (MOFs), specifically ZIF-8, ranging from the nanometer scale to the micrometer scale (800 nm to 110 μm). Additionally, we successfully cultivated ZIF-8 on both sides of a single-mode fiber (SMF) with thicknesses of 25 μm and 50 μm. In a separate experiment, we successfully grew ZIF-8 on one side of an optical fiber, achieving a thickness of 10 μm. The sensor demonstrated notable sensitivity to ethanol, with the fringe valley shifting from 1602 nm to 1606.8 nm as the ethanol concentration increased from 30 ppm to 70 ppm. Reducing the thickness of the MOF coating led to notable improvement in response and recovery times. Specifically, for a 10 μm cavity length, response time decreased to around 17 seconds and recovery time to 50 seconds, compared to 110 μm cavities which took 1 minute to respond and 4 minutes to recover at room temperature.