Plasmonic CH ₄ Sensor Based on MIM Waveguide Coupled to Circular Nanorod in a Square‐Shaped Cavity

ABSTRACT A novel refractive index (RI) plasmonic sensor is designed and simulated, which is expected to make a significant advancement in gas sensing. The sensor is composed of silver, air‐filled waveguide and a square shaped cavity. In the implemented cavity, 16 silver circular nanorods (CNs) are locally placed to enhance the sensing performance. Moreover, the cavity is filled with ultraviolet‐curable fluoro‐siloxane (UVCFS) in order to faithfully characterise methane gas concentrations. RI sensitivity (RIS) for Peak I is 1210.12 ± 4.62 nm/RIU and for Peak II is 969.64 ± 8.56 nm/RIU as well as figure of merit (FoM) of 20.00 ± 0.08 1/RIU at Peak I and 11.82 ± 0.10 1/RIU at Peak II, respectively. Furthermore, a significant methane gas sensitivity ( S Gas ) is achieved: about 4 nm/% for Peak I and about 3 nm/% for Peak II which shows that it can well determine methane gas concentrations. The introduced plasmonic‐based sensor brings potential applications in gas sensing due to its high sensitivity as well accuracy in detecting methane gas concentrations.