Directional terahertz holography with thermally active Janus metasurface

Abstract

Dynamic manipulation of electromagnetic (EM) waves with multiple degrees of freedom plays an essential role in enhancing information processing. Currently, an enormous challenge is to realize directional terahertz (THz) holography. Recently, it was demonstrated that Janus metasurfaces could produce distinct responses to EM waves from two opposite incident directions, making multiplexed dynamic manipulation of THz waves possible. Herein, we show that thermally activated THz Janus metasurfaces integrating with phase change materials on the meta-atoms can produce asymmetric transmission with the designed phase delays. Such reconfigurable Janus metasurfaces can achieve asymmetric focusing of THz wave and directional THz holography with free-space image projections, and particularly the information can be manipulated via temperature and incident THz wave direction. This work not only offers a common strategy for realizing the reconfigurability of Janus metasurfaces, but also shows possible applications in THz optical information encryption, data storage, and smart windows.

Tunable VO2 cavity enables multispectral manipulation from visible to microwave frequencies

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Wide-angle camouflage detectors by manipulating emissivity using a non-reciprocal metasurface array

“…For practical purposes, radiation camouflage is more promising because the radiative properties can be modulated based on the surface characteristics, whether they are flattened, curved, smooth, rough or flexible. [19][20][21][22] It is possible to modulate the spectral, spatial, and polarization characteristics of thermal radiation, [23][24][25][26][27][28][29][30][31][32][33][34][35] using nanostructures such as photonic crystals, gratings, multi-layered structures, meta-materials, and metasurfaces. For all proposed nanophotonic camouflage designs, emissivity is required to be near zero in the atmospheric window (8 mm to 14 mm), which is transparent to radiation and prone to detection.…”