Hydrogen sensor based on surface plasmon polaritons in palladium layer structure

We design a new hydrogen (H 2 ) sensor composed of palladium (Pd) layer structure. Pd can absorb H 2 and turns to Pd-H. The dielectric constant of Pd is totally different from the one of Pd-H. By calculating the propagation length of the layer structure, we find that the difference of the propagation lengths between the structure with Pd and the structure with Pd-H reaches ten times the wavelength in a certain condition. With the number of the layers increasing, another new mode appears and the dissipation of our proposed structure also linearly increases. There is a worst number of the layers that make the difference of the propagation lengths shortest. This shows the competition between the dissipation of the structure and the coupling of surface plasmon polaritons among the layers. In order to achieve the function of H 2 detecting, we set the length of the structure at minimum of L Pd and at a certain working wavelength. By adding the concentration of H 2 , light will emit or not emit . Our proposed technique has a large difference of propagation lengths and is quite sensitive to H 2 , which can be used as a hydrogen sensor.