Abstract
Metamaterial absorber/emitter is an important aspect of infrared radiation manipulation. In this paper, we proposed four simple switchable infrared metamaterial absorbers/emitters with Ag/VO2 disks on the Ag plane employing triangle, square, hexagon, and circle unit cells. The spectral absorption peaks whose intensities are above 0.99 occur at ~4 μm after structure optimization when VO2 is in insulating state and disappear when VO2 becomes metallic state. The simulated electromagnetic field reveals that the spectral absorption peaks are attributed to the excitation of magnetic polariton within the insulating VO2 spacer layer, whose values exceed 1.59 orders of magnitude higher than the incident magnetic field. Longer resonant wavelength would be excited in square arrays because its configuration is a better carrier of charges at the same spans. For absorption stability, the absorbers/emitters with square and circular structures do not have any change with the polarization angles changing from 0° to 90°, due to the high rotational symmetric structure. And four absorbers/emitters reveal similar shifts and attenuations under different incident angles. We believed that the switchable absorber/emitter demonstrates promising applications in the sensing technology and adaptive infrared system.
Highlights
An object would absorb radiation from surrounding space and reradiates internal energy to outside, and the values of that are determined by its temperature and electromagnetic (EM) wave frequency, as described by Planck’s law [1]
The mechanisms of spectral absorption peaks are the excitation of magnetic polariton (MP) or standing waves, or other kinds of resonances
We focus on MP in insulating VO2 between the upper patches of Ag and the lower Ag plane when VO2 is in insulating state, which frequently occurred within a metal-insulator-metal structure
Summary
An object would absorb radiation from surrounding space and reradiates internal energy to outside, and the values of that are determined by its temperature and electromagnetic (EM) wave frequency, as described by Planck’s law [1]. Zhu et al designed thermal management devices by combining wavelength-selective emitters and thermal insulators and achieved emittance of ~0.58 and~0.08 within 5-8 and 8-14 μm, reducing the surface temperature of a high-temperature object (873 K) to 410 K [8]. An alternative approach to achieve selective emitters is metamaterial absorbers/emitters, which possess high absorptance at specific wavelengths, and it has been attracted great attention for radiation regulation applications. An acceptable explanation of perfect absorption is the impedance of metamaterial that would be equivalent to the outside. It means perfect absorption could be achieved through extraordinary structural design for a specific frequency [9,10,11].
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