Enhanced H2S gas sensing using Ta2O3/Au bilayer SPR sensor with semicircular prism configuration

A high-sensitivity surface plasmon resonance (SPR) gas sensor based on a Ta 2 O 3 /Au bilayer integrated with a semicircular prism is experimentally demonstrated. By using the Kretschmann configuration with a BK7 prism, to significantly improve how light couples with the surface plasmons. The fabricated Au and Ta 2 O 3 thin films were deposited using the DC magnetron sputtering method, optimizing their thicknesses to the 20/50 nm. The sensing of H 2 S gas was investigated using a He–Ne laser (λ = 632.8 nm) by measuring the changes in the reflected intensity and incident resonance angle. The semicircular prism design offered an advantage over traditional triangular geometries, specifically, it achieved a maximum sensitivity of 31%, representing a 13% improvement in performance. This improvement is attributed to enhanced field confinement and reduced optical losses due to the prism geometry, which leads to stronger interaction between the plasmons and the gas at the interface layer. Furthermore, the high refractive index of the Ta 2 O 3 layer allows the evanescent field to penetrate deeper, making the sensor more responsive to refractive index changes. Ultimately, this structure provides a practical, simple, and efficient way to enhance the SPR gas sensor for environmental monitoring applications.