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In this paper, a polarization selective broad/triple-band metamaterial absorber based on SiO2 all-dielectric is designed and studied. The absorber works in a long infrared band (8–14 μm). It is composed of cuboid and trapezoidal silica structures in the upper layer and metal plates in the lower layer. We calculate the absorption results of the metamaterial absorber at different polarization angles as the polarization angle of incident light increases from 0° to 90°; that is, the light changes from Ex polarization to Ey polarization. The results show that the absorption rate of the structure is more than 90% in the range of 8.16 to 9.61 μm when the polarization angle is 0°. When the polarization angle of the incident light is less than 45°, the absorption result of the absorber does not change significantly. When the polarization angle of the incident light is greater than 45°, three absorption peaks appear in the long infrared band, realizing the selectivity of the polarization of the incident light. When the polarization angle increases to 90°, the absorptivity of the two absorption peaks at λ = 9.7 μm and 12.3 μm reaches more than 85%. In addition, the sensitivity analysis of the length, width, and thickness of the all-dielectric metamaterial absorber and the calculation of the electric field of this structure are also carried out. The designed all-dielectric metamaterial absorber has polarization selection and perfect absorption characteristics and has a broad application prospect.

A relative humidity sensor based on a silver nano-grating was proposed. By stripping and cleaning commercially available CD and DVD discs, polycarbonate plates with different grating periods are obtained. These plates as templates are coated with a layer of sputtered silver film to form silver nano-gratings, which exhibit refractive index sensing sensitivities of 517 nm/RIU and 742.9 nm/RIU, respectively. The finite-difference time-domain simulation results conform the excited surface plasmon polariton modes and localized surface plasmon modes on the nano-grating. By spin coating a layer of humidity-sensitive porous silica with optimized thickness, the silver nano-grating shows a relative humidity detection sensitivity of 0.23 nm/%RH.