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Geometric metasurfaces have shown superior phase control capacity owing to the geometric nature of their phase profile. The existing geometric metasurfaces are generally composed of metal-dielectric composites or all-dielectric subwavelength structures. Here, a novel configuration, all-metallic structure, is proposed to achieve broadband and high-performance electromagnetic wavefront manipulation based on the geometric phase. A catenary model is built to describe the optical dispersion and guide the design of metasurfaces. Two metadevices including a beam deflector and a hologram are designed and experimentally demonstrated in the infrared regime, with the measured optical efficiency up to 84% (the simulated efficiency reaches 93%). Compared to previous metal-insulator-metal structures, this approach can realize higher efficiency and broader operating bandwidth owing to its lower ohmic loss. This design strategy is universal and can be easily scaled to any other spectra without complex optimization. Moreover, since metals have excellent mechanical and physical properties, such as good thermal and electrical conductivity, this all-metallic structure may provide a new thinking on interdisciplinary research.

Optical camouflage is a magical capability of animals as first noticed in 1794 by Erasmus Darwin in Zoonomia, but current biomimetic camouflage strategies cannot be readily applied in complex environments involving multispectral and in particular multi-polarization detection. Here we develop a plasmonic approach toward broadband infrared polarimetric crypsis, where the polarized thermal emission near the pseudo-Brewster angle is the main signal source and no existing polarizing camouflage technique has been discovered in nature. Based on all-metallic subwavelength structures, an electrodynamic resistance-reduction mechanism is proposed to avoid the significant polarization-dependent infrared absorption/radiation. It is also found that the structured metal surface presents giant extrinsic anisotropy regarding the phase shift between orthogonal polarization states, which helps to realize ultrahigh-efficiency and tunable polarization conversion in an unprecedented manner. Finally, we note that the catenary optical theory may provide a useful means to explain and predict these unusual performances.

Geometric metasurfaces have shown superior phase control capacity owing to the geometric nature of their phase profile. The existing geometric metasurfaces are generally composed of metal-dielectric composites or all-dielectric subwavelength structures. Here, a novel configuration, all-metallic structure, is proposed to achieve broadband and high-performance electromagnetic wavefront manipulation based on the geometric phase. A catenary model is built to describe the optical dispersion and guide the design of metasurfaces. Two metadevices including a beam deflector and a hologram are designed and experimentally demonstrated in the infrared regime, with the measured optical efficiency up to 84% (the simulated efficiency reaches 93%). Compared to previous metal-insulator-metal structures, this approach can realize higher efficiency and broader operating bandwidth owing to its lower ohmic loss. This design strategy is universal and can be easily scaled to any other spectra without complex optimization. Moreover, since metals have excellent mechanical and physical properties, such as good thermal and electrical conductivity, this all-metallic structure may provide a new thinking on interdisciplinary research. [ABSTRACT FROM AUTHOR]

Manipulating multispectral electromagnetic (EM) waves has drawn great attention due to its potential applications in EM compatibility, radiative cooling, and multispectral imaging. Metasurfaces are intensively investigated to control EM waves and achieve versatile functions. However, the design of multispectral manipulation and the fabrication of multiscale metasurfaces remain a great challenge. Here, a multiscale flexible metasurface with nanometer‐sized characteristic dimensions and a square centimeter sized area is designed and fabricated for the simultaneous manipulation of infrared and terahertz waves. A simple yet powerful analytic method derived from catenary field theory is proposed to guide the design. A metasurface consisting of 2D nanoslit array is fabricated onto a flexible polyimide substrate by combining shadow mask fabrication with surface plasmon lithography to achieve nanoscale, large‐area, and repeatable fabrication. The experimental results show that the proposed metasurface possesses high reflectance exceeding 95% within the 8–12 µm wavelength range, indicating low thermal emissivity. Additionally, the metasurface exhibits low reflection in the THz regime and is capable of implementing integrated functions in conjunction with THz devices. Furthermore, the significant advantage of flexibility affords the metasurface excellent compatibility with irregular surfaces. This work may provide important guidance for the design and fabrication of large‐scale multispectral metasurfaces. [ABSTRACT FROM AUTHOR]

Self‐accelerating beams have drawn enormous attentions in optics owing to their nondiffracting and self‐healing properties. Traditionally, the generation of such beams demands bulky devices and a long working distance, which impede the miniaturization of the optical system. Recent progresses in metasurfaces facilitate replacing cumbersome optical components by ultrathin and planar nano‐optical devices. Nevertheless, most of the existing approaches suffer from fixed trajectories, narrow operation bandwidth and low efficiency. Here, a methodology is proposed to generate self‐accelerating beams with arbitrary profiles by employing a generalized analysis based on geometric optics and interference theory. As a proof of the concept, single catenary‐shaped metasurface is utilized to generate the cubic phase shift, which leads to a reciprocal accelerating trajectory. The spatially continuous and spectrally dispersionless catenary nanoapertures show great advantages in terms of bandwidth and efficiency over discrete counterparts. The polarization‐controlled accelerating trajectories are demonstrated by both simulations and measured results. The proposed compact and efficient beam generators are believed to be promising for future on‐chip and integration applications. [ABSTRACT FROM AUTHOR]

Catenary functions are exciting and fundamental building blocks in constructing various kinds of waves in subwavelength structures. Here, a simple yet powerful approach inspired by catenary optics is proposed to realize efficient manipulation of electromagnetic waves in terms of both amplitude and phase. By properly engineering the catenary electromagnetic fields and frequency dispersion, lightweight metafilm‐based broadband absorbers with polarization‐independent bandwidth covering 0.65–6.2 GHz are experimentally achieved, and the bandwidth is further broadened to 0.9–40 GHz. With the same approach, a large‐scale flat antenna based on generalized reflection is demonstrated in the satellite communication system. To enable the batch manufacturing, a flexible substrate–based microfabrication process is developed with a minimum feature size of down to sub‐micrometer and total size up to almost 1 m. These results may provide important guidance for the design of metasurface‐based devices. A systematic, general way to achieve efficient design of flat electromagnetic devices based on the catenary model is demonstrated. By employing the proposed method, broadband absorbers and flat antennas are experimentally achieved with lightweight properties and higher efficiencies compared with their traditional counterparts. Besides, a film‐based microfabrication process is developed to enable batch manufacturing for these devices. [ABSTRACT FROM AUTHOR]

Catenary functions are exciting and fundamental building blocks in constructing various kinds of waves in subwavelength structures. In article number 1801691, Xiangang Luo and co‐workers propose a simple yet powerful approach to realize efficient design of metasurfaces inspired by catenary electromagnetics. By employing this methodology, flexible‐substrate‐based large‐scale broadband absorbers and flat antennas are experimentally achieved with lightweight properties and outstanding operation performances. [ABSTRACT FROM AUTHOR]

In article number 1800612, Xin Xie, Xiangang Luo and co‐workers demonstrate an all‐metallic metasurface skin for achieving broadband and wide‐angle radar cross section reduction. The catenary optical fields and dispersion in the space‐variant metallic gratings help to significantly broaden the operating bandwidth. This approach may provide a feasible alternative for surface coating in conformal camouflage applications. [ABSTRACT FROM AUTHOR]

Metallic skins are widely used in practical engineering owing to their inherent advantages in mechanical and physical characteristics. In this paper, a metasurface skin composed of subwavelength metallic gratings with space‐variant orientations has been proposed to realize exotic electromagnetic properties in microwave and infrared regimes. Equivalent circuit theory and transfer matrix method have been adopted to quantitatively describe the optical fields and dispersion with high accuracy in a catenary form. Based on these analyses, broadband and wide‐angle radar cross‐section (RCS) reduction for microwave has been simulated and experimentally demonstrated. Additional characteristics such as high temperature resistance and low infrared thermal emission are also verified. It is believed that these results may provide a new platform to achieve multifunctional electromagnetic devices and are promising for many applications. A heat resisting all‐metallic metasurface is reported to simultaneously achieve broadband microwave radar cross‐section reduction and thermal infrared invisibility. Compared to previous scattering engineered metasurfaces based on metal–insulator–metal composites, this approach not only demonstrates the advantages such as high efficiency, easy‐fabrication, and multifunctionality but also shows excellent mechanical and physical advantages involving high temperature resistance, great durability, etc. [ABSTRACT FROM AUTHOR]

Metasurfaces with intense spin–orbit interactions (SOIs) offer an appealing platform for manipulation of polarization and wavefront. Reconfigurable beam manipulation based on switchable SOIs is highly desired in many occasions, but it remains a great challenge since most metasurfaces lack the flexibility and the optical performance is fixed once fabricated. Here, switchable SOIs are demonstrated numerically and experimentally via the combination of plasmonic metasurfaces with phase change materials (PCMs). As a proof‐of‐concept, three metadevices possessing switchable SOIs are fabricated and investigated, which enable spin Hall effect, vortex beam generation, and holography when the PCM is in the amorphous state (corresponding to the "ON" state of SOI). When the PCM changes into the crystalline state (corresponding to the "OFF" state of SOI), these phenomena disappear. Experimental measurements show that a high polarization conversion contrast between "ON" and "OFF" states is obtained within a broadband wavelength range from 8.5 to 10.5 µm. The switchable photonic SOIs proposed here may provide a promising route to design reconfigurable devices for applications such as beam steering, dynamic holographic display, and encrypted optical communications. Metadevices with switchable spin‐orbit interactions offer an appealing platform for dynamic and reconfigurable beam manipulation which is one important developing trend in photonic devices. Here, such devices are experimentally demonstrated via the combination of plasmonic metasurfaces and phase‐change materials. It is believed that this work made a major step forward to achieve on‐demand beam manipulation. [ABSTRACT FROM AUTHOR]

Metasurfaces with switchable spin–orbit interactions (SOIs) offer an appealing platform for dynamic and reconfigurable beam manipulation. In article number 1800835, Xiangang Luo and co‐workers demonstrate switchable SOIs experimentally via the combination of plasmonic metasurfaces with phase change materials (PCMs). The metadevices with switchable SOIs provide a promising route to achieve reconfigurable applications such as encrypted optical communications and dynamic holographic displays. [ABSTRACT FROM AUTHOR]