A Dual-Band Polarization Insensitive Metamaterial Absorber with a Single Square Metallic Patch for Sensing Application

We proposed a dual-band polarization-insensitive metamaterial absorber consisting of merely the square metallic patch and a continuous metallic ground separated by a middle dielectric layer. Two resonance peaks derived from `the fundamental resonance (with 97% absorbance) and the surface lattice resonance (with 99% absorbance) are realized. It is different from previous work that the dual-band response is obtained by combining two resonances of different sizes. Moreover, a first-order diffraction mode of grating predicts the resonance wavelength of the proposed absorber. The surface electromagnetic field distributions of the unit-cell structure reveal the physical origin of the dual-band absorption. Importantly, the first absorption peak results from surface lattice resonance with narrow line-width has large sensitivity perform and high-quality factor, which has significant potential in the application of the biosensors and monitoring.