Rounding corners of nano-square patches for multispectral plasmonic metamaterial absorbers

Abstract

Multispectral metamaterial absorbers based on metal-insulatormetal nano-square patch resonators are studied here. For a geometry consisting of perfectly nano-square patches and vertical sidewalls, double resonances in the visible regime are observed due to simultaneous excitation of electric and magnetic plasmon modes. Although slightly modifying the sizes of the square patches makes the resonance wavelengths simply shift, rounding corners of the square patches results in emergence of a third resonance due to excitation of the circular cavity modes. Sidewall angle of the patches are also observed to affect the absorption spectra significantly. Peak absorption values for the triple resonance structures are strongly affected as the sidewall angle varies from 90 to 50 degrees. Rounded corners and slanted sidewalls are typical imperfections for lithographically fabricated metamaterial structures. The presented results suggest that imperfections caused during fabrication of the top nanostructures must be taken into account when designing metamaterial absorbers. Furthermore, it is shown that these fabrication imperfections can be exploited for improving resonance properties and bandwidths of metamaterials for various potential applications such as solar energy harvesting, thermal emitters, surface enhanced spectroscopies and photodetection.

Tri-band absorption enhancement in monolayer graphene in visible spectrum due to multiple plasmon resonances in metal–insulator–metal nanostructure

“…3(a) and 3(b), there are six noticeable field hotspots around the edge of the Ag nanodisk, which directly indicates the excitation of a circular cavity mode at the resonance wavelengths of λ 1 . 48) In Fig. 3(c), two obvious electric-field hotspots on the left and right sides of the Ag nanodisk are observed, which are surrounded by four significantly weaker linear hotspots.…”

“…Such a field distribution implies the excitation of a higher-order magnetic plasmon mode. 48) The aforementioned resonance modes result from the interference of surface plasmons inside the SiO 2 gap between the Ag nanodisk and the substrate, which forms standing electromagnetic waves. The z component E z of the electrical field inside the gap is dominant and can be approximately solved using the following Helmholtz equation in cylindrical coordinates: 53)…”

Polarization-selective absorbers made of MDM metamaterials for infrared source emission

“…Coherent light sources in the infrared region are important in communications, military, biomolecular, medical, and laser technologies. [1][2][3][4][5] However, coherent light sources in the infrared are too scarce which limits their usage. Wonderful accomplishments have been made using coherent infrared light sources through deliberately designed optical structures such as quantum cascades, quantum wells, quantum dots and some gas lasers.…”