Camouflage is an emerging application of metamaterials owing to their exotic electromagnetic radiative properties. Based on the use of a selective emitter and an absorber as the metamaterials, most reported articles have suggested the use of single‐band camouflage, however, multispectral camouflage is a challenging issue owing to a difference of several orders of magnitude in the unit cell structure. Herein, hierarchical metamaterials (HMMs) for multispectral signal control when dissipating the absorbed energy of microwaves through the selective emission of infrared (IR) waves from the unit cell structure of the HMM are demonstrated. Integrating an IR selective emitter (IRE) with a microwave selective absorber, multispectral signal control with the large‐sized unit cell structures of up to 10 cm are realized. With an IRE, the emissive power from the HMM toward 5–8 µm is 1570% higher than the Au surface, which is preventing the occurrence of thermal instability. Furthermore, we determine that the signature levels of targeted IR waves (8–12 µm) and microwaves (2.5–3.8 cm) are reduced by up to 95% and 99%, respectively, when applying the HMM.
Artificial camouflage
surfaces for assimilating with the environment
have been utilized for controlling optical properties. Especially,
the optical properties of infrared (IR) camouflage materials should
be satisfied with two requirements: deception of IR signature in a
detected band through reduced emissive energy and dissipation of reduced
emissive energy for preventing thermal instability through an undetected
band. Most reported articles suggest the reduction of emissive energy
in the detected band; however, broadband emission for enough energy
dissipation through the undetected band simultaneously is still a
challenging issue. Here, we demonstrate the multiresonance emitter
for broadband emission with IR camouflage utilizing the electromagnetic
properties of dielectric material. We reveal that the interaction
between the magnetic resonance and dielectric layer’s property
in a metal–dielectric–metal structure induces the multiple
resonance at the specific band. We present an IR camouflage behavior
of multiresonance emitter on a curved surface through the IR camera
(8–14 μm). We evaluate the energy dissipation in the
undetected band, which is 1613% higher than metal and 26% higher than
conventional selective emitters. This study paves the way to develop
broadband emitters for radiative cooling and thermophotovoltaic applications.
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