Coal mine methane monitoring is one of the important measures to ensure mine safety. A terahertz absorber based on an electromagnetic metasurface is designed to realize real-time monitoring of methane gas in coal mines.The design of the metasurface absorber structure enables efficient absorption at specific frequencies such as methane characteristic absorption peaks.The absorber is based on a dual-frequency terahertz metasurface structure consisting of a rectangular ring and a cross-shaped gallium arsenide (GaAs) material

achieving perfect absorption at frequencies of 0.6 and 1.2THz.The absorption characteristics of the absorber are influenced not only by the geometric dimensions of the structure but also are sensitive to the refractive index of the surrounding gas.The application of the proposed absorber in coal mine methane gas monitoring is investigated

and the impact of refractive index variation caused by methane concentration change on the absorption peak of the absorber is analyzed.The unit refractive index sensitivity is 0.13 and 0.27THz/RIU at 0.6 and 1.2THz

respectively.The metasurface absorber has fast response speed

enabling real-time monitoring of methane concentration changes and helping to detect potential hazards in a timely manner.The terahertz metasurface absorber proposed in this paper has high sensitivity

is easy to integrate

and has strong real-time capability

showing potential applicability in the field of coal mine methane gas monitors.