A Novel Hydrogen Sensor Based on a Guided-Mode Resonance Filter

In this study, we demonstrated a hydrogen (H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) sensor based on a guided-mode resonance (GMR) filter coated with a layer of palladium (Pd). The sensor consists of three key layers, namely the substrate (replicated grating structure on an optical adhesive), waveguiding layer of TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , and active-sensing layer of Pd. The sensor functions as an optical resonator. On absorption of H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , the change of the refractive index in Pd changes the optical response of the sensor. To monitor the output optical response, a transmission setup was used, and two detection modalities-the change in transmission efficiency at a specific wavelength and the shift in the resonant wavelength-were demonstrated. Upon injection of a mixture of 4% H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and 96% argon, the resonant wavelength shifted 6.38 nm, and transmission efficiency increased by 45% in 24 s.