Design of Transparent Metasurfaces Based on Asymmetric Nanostructures for Directional and Selective Absorption

Abstract

Maximizing the solar heat gain through windows in winter and minimizing the solar radiation entering the room in summer are of great significance for the energy saving of buildings. Here, we present a new idea for transparent metasurfaces, based on asymmetric metal/insulator/metal (MIM) nanostructures, which can be switched back and forth between absorbing and reflecting solar radiation by reversing the sample orientation. Owing to the fundamental mode of a low-quality-factor resonance, a selective near-infrared absorption is obtained with an absorption peak value of 90% upon front illumination. The average solar absorption (45%) is about 10% higher than that (35%) of reported transparent absorbers. The near-infrared light is also strongly and selectively reflected upon back illumination and a reflection peak value above 70% is observed. Meanwhile, the average visible transmission of the metasurface is above 60%, which is about 1.6 times that (36%) of previous transparent metasurface absorbers. In addition, Cu material can replace the noble metals in this work, which will greatly reduce the manufacturing cost. Owing to the attractive properties of directional and selective absorption, passive operation mode, and low cost of the materials, the metasurfaces have promising prospects in building energy saving or other solar applications where surface transparency is desirable.

Photonic Multilayer Structure Induced High Near‐Infrared (NIR) Blockage as Energy‐Saving Window

“…Metasurfaces based on subwavelength scale nanostructure absorb NIR by using Mie resonance. [4][5][6][7][8][9][10][11][12][13][14][15][16] However, the absorbed solar energy acts as with calculated results. The NIR-blocking effectiveness of the designed multilayer film exceeds those of previously-reported other technologies such as metasurfaces, D/M/Ds, thin-film structures and organic coatings by employing an extra TiO 2 back reflector layer.…”

“…NIR-blocking films have been developed using several techniques such as metasurface, [4][5][6][7][8][9][10][11][12][13][14][15][16] D/M/D films, [24][25][26][27][28] and thin films, [41][42][43] organic coatings [44][45][46][47][48][49][50][51] (Table 1). NIR blocking metasurfaces are divided into opaque and transparent types.…”

“…Transparent metasurfaces have high visible transmittance (>60%). [14][15][16] But most are undesirable as an energy-saving film because they absorb solar energy that can be used as an additional heat source. In addition, metasurfaces require complicated fabrication processes such as e-beam lithography.…”

“…Metasurfaces based on subwavelength scale nanostructure absorb NIR by using Mie resonance. [ 4–16 ] However, the absorbed solar energy acts as an additional heating source, which can reduce cooling effects. The thick metal film can block NIR by reflection rather than absorption.…”

Mechanical Shunt Resonators-Based Piezoelectric Metamaterial for Elastic Wave Attenuation

“…Phononic crystals and metamaterials have attractive potential in elastic wave manipulation and attenuation [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ]. They show promising advantages in the applications of negative refraction [ 2 , 3 ], acoustic cloaking [ 4 , 5 ], wave focusing [ 6 , 7 , 8 , 9 , 10 ], wave attenuation [ 11 , 12 , 13 , 14 , 15 , 16 , 17 ], and vibration-mode tailoring [ 18 ]. The features of phononic crystals and metamaterials stem from Bragg scattering and local resonance, respectively [ 19 , 20 , 21 , 22 , 23 ].…”