The original version of this article unfortunately contained a mistake. The name of the fourth author is written reversely. The complete name of the fourth author is as follows: "Andriy E." as the first name, while "Serebryannikov" is his last name. The original article has been corrected.Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Wavelength-selective nanoantenna emitters have attracted considerable attention due to their widespread applications ranging from thermal radiation management to thermophotovoltaics. In this paper, we design a wavelength-selective nanoantenna emitter based on the excitation of gap-surface plasmon modes using a metal-insulator-metal configuration (silicon dioxide (SiO 2 ) sandwiched between silver (Ag) layers) for satisfying multiple infrared applications. The proposed design, which is called design I, realizes triple narrowband perfect absorptions at the resonance wavelengths of 1524 nm, 2279 nm, and 6000 nm, which perfectly match the atmospheric absorption bands while maintaining relatively low emissivity in the atmospheric transparency windows of 3−5 µm and 8−12 µm. Later, the functionality of design I is extended, which is called design II, to include a broadband absorption at the near-infrared region to minimize the solar irradiation reflection from the nanoantenna emitter. Finally, singleand three-layer graphene are introduced to provide a real-time tuning of the infrared signature of the proposed nanoantenna emitter (design II). It is also demonstrated that the three-layer graphene structure can suppress an undesired absorption resonance wavelength related to the intrinsic vibrational modes (optical phonons) of the SiO 2 layer by 53.19% compared to 25.53% for the single-layer one. The spectral analysis of design I is validated using both analytical and numerical approaches where the numerical simulation domain is extended for the analysis of design II. The thermal characteristic analyses of design I and design II (without/with graphene layers) reveal that infrared signatures of the blackbody radiation are significantly reduced for the whole wavelength spectrum at least by 96% and 91% within a wide temperature ranging from room temperature to 500 K, respectively.
In modern warfare, multi-spectral camouflage must be developed to conceal the thermal signature of an object. In general, camouflage needs to be satisfied in two main optical ranges: visible, and infrared (IR). In IR range, two main camera modes are deployed to detect the IR signature of an object: i) short-wave-IR (SWIR) cameras that detect the solar photons reflected off a surface, ii) mid-wave-IR (MWIR) and long-wave-IR (LWIR) cameras that directly collect the blackbody photons emitted from a hot object. Therefore, in an ideal scheme to acquire a multi-spectral camouflage function with self-cooling capability, the object should have: i) perfect absorption in the SWIR range, ii) perfect reflection in the MWIR and LWIR ranges, iii) perfect absorption and one-way transmission in non-transmissive IR (NTIR) windows (to radiatively cool itself), and iv) visible transparency (to keep background visual appearance intact and to minimize the heat build-up due to solar absorption). In this paper, an all-dielectric nanoantenna emitter design has been developed to comply with all the above requirements. The approach relies on the indium tin oxide (ITO) grating structures coated on a flexible and transparent substrate (polystyrene). The spectral behaviors of the proposed structure are obtained using both analytical and numerical approaches. The design has an absorption peak with 0.8 amplitude in SWIR mode (for the backward and forward illuminations), while it shows > 0.7 average reflections in the MWIR and LWIR ranges for the backward illumination. The peak values of transmission and absorption within the NTIR window for the backward illumination are around 0.6 and 0.9, respectively. Meanwhile, the use of lossless materials within the visible range provides visible light transmission and minimizes the heat build-up due to solar absorption. In addition, the radiated power calculation model is utilized to demonstrate the low power detection on the infrared cameras.INDEX TERMS Binary grating, Metamaterial, Nanoantenna emitter, Plasmonic, Thermal camouflage I. INTRODUCTIONCamouflage technology is developed to conceal the signature of an object from potential threats. However, the advancement in sensors pushed this field to multi-spectral camouflage requirements in order to cover the multiple detection scenarios [1]-[3]. In general, camouflage needs to be satisfied in two main wavelength ranges; i) visible, and ii) infrared (IR). For the visible range, the use of pigments with proper coloration can provide visual camouflage via imitating the surrounding background or by resembling something else. However, for the IR case, we need to cover multiple detection ranges to mitigate the IR signature of an object without disturbing the visible appearance.According to Planck's radiation law [4], [5], a blackbody in thermal equilibrium with a temperature above the absolute zero spontaneously and continuously emits electromagnetic
We present a narrow-band optical diode with a high-contrast forward-to-backward ratio at the near-infrared region. The design has a forward transmission of approximately 88%, and a backward one of less than 3%, yielding a contrast ratio of greater than 14.5 dB at a wavelength of 1550 nm. The structure is composed of a one-dimensional diffraction grating on top of a dielectric slab waveguide, both of which are made of silicon nitride (Si 3 N 4 ), and all together are placed over a silver (Ag) thin film embedded on a dielectric substrate. Utilizing a dielectric-based diffraction grating waveguide on a thin silver layer leads to the simultaneous excitation of two surface plasmon modes known as long-and short-range surface plasmon polaritons (SPPs) at both interfaces of the metallic layer. The plasmon-tunneling effect, which is the result of the coupling of SPPs excited at the upper interface of the metallic layer to the radiation modes, provides a high asymmetric transmission (AT) property. The spectral response of the proposed high-contrast AT device is verified using both rigorous coupled-wave analysis as an analytical approach and finite difference time domain as a numerical one.
Metamaterial nearly perfect light absorbers (MPAs) with dual-narrowband functionality—that absorb light in two narrowband adjacent wavelength regions—have attracted considerable attention due to their intriguing applications, such as sensing, photovoltaic, and thermal emission. Here, we propose a multi-band MPA with two narrowband absorption responses that are centered on the visible and near-infrared (NIR) wavelengths (773 nm and 900 nm, respectively) and a broadband absorptive characteristic in another window in the NIR region (ranging from 1530 nm to 2700 nm with a bandwidth of 1170 nm). The MPA comprises a periodic array of self-aligned hybrid indium tin oxide (ITO)-Au split-ring-resonators that are separated from an optically thick bottom reflector with a SiO2 layer. Based on numerical calculations, which are accompanied with a semi-analytical examination, we find that the dual narrowband and broadband responses are attributed to the hybridization of the optical responses of gold as a plasmonic material with the ones of ITO. Note that ITO acts as a low-loss dielectric in the visible range and a lossy plasmonic material in the NIR region. Moreover, due to the applied symmetry in the unit cell of the metamaterial, the proposed MPA represents polarization insensitive and omnidirectional absorptive features. The proposed metastructure can find potential applications in selective thermophotovoltaic devices, thermal emitters, and sensors.
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