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In this paper, we proposed a perfect absorber composed of a periodic double-layer graphene ribbon arrays placed on a metallic reflector separated by a dielectric layer for infrared sensing. The anti-symmetric dipole-dipole coupling mode is excited as the impedance matchingCnar-rowband absorption spectrum. Numerical simulations show that the absorption and reflection properties of the absorber are sensitive to the refractive index of the surrounding medium. Furthermore, the plasmon resonance wavelength can be tuned by varying the Fermi energy level of graphene. Such a plas-monic absorber with high sensitivity can be beneficial for chemical and biosensor applications.

In this paper, a heterogeneous Au-Ag nanostructure consisting of a rod and concentric square ring-disk is pro-posed to generate intense plasmonic Fano resonances. And the Fano resonance in plasmonic nanostructures is produced by the coupling between broad bright mode and narrow dark mode, causing a Fano dip in the scattering spectrum. One of the main characteristic of the Fano dip is the line width which can be reduced to 0.0135 eV in this nanostructure, and the local electric field enhancement factor can reach 64, which enables its promising applications in biosensing, detecting and surface-enhanced Raman scattering.

An electrically controlled superresolution filter is proposed for the manipulation of transverse superresolution performance and axial focal shift. It consists of two parallel polarizers and a four-zone electro-optic crystal. The spatial manipulation of the polarization state and intensity can be realized by voltage applied on this four-zone electro-optic crystal. The redistribution of the filtered intensity near the focus is calculated. The axial focal shift and the transverse superresolution can be obtained and adjusted in particular parameters including radius, azimuth angle and proper applied voltage.