Highly integrated hydrogen sensor based on inverse surface plasmon polaritons

We report a novel hydrogen sensor based on inverse surface plasmon polaritons (ISPPs) which may be used in integrated optical circuit. If a light beam hits a prism with Kretschmann configuration at a proper angle, the surface plasmon polaritons (SPPs) will be excited at the surface of the metal film. And the angle depends on the optical properties of the film. We use a palladium (Pd) film which changes its dielectric function in hydrogen gas. Thus, the incident angle can be used to indicate the concentration of hydrogen. Our sensor inverted all the process: SPPs are excited by a grating integrated on the Pd film, and decoupled by the prism, the angle of departure will indicate the hydrogen concentration. According to our simulation, if the concentration of hydrogen increases by 1%, the angle changes by and the intensity decreases by 1.55%. Our proposal can be used to improve the integration of ISPPs sensors.