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Nanoantennas and their arrays (metasurfaces) provide a versatile platform for controlling the coherence of thermal emission. Conventional designs rely on global heating, which impedes emission efficiency and on-chip integration. In this work, we propose an electrically driven metasurface composed of a Yagi-Uda nanoantenna array interconnected by S-shaped electrode wires, which enables the concurrent manipulation of thermal emission spectrally and directionally. A direct simulation approach based on the Wiener-chaos expansion method is employed for quantitative analysis. Our metasurface device exhibits a narrowband emission with high directivity, which is one order higher than that of a single nanorod antenna case. The modeling framework established in this work opens a promising route for realizing coherent mid-infrared emission by metasurfaces. 

Plasmonic metasurfaces with adjustable optical responses can be achieved through phase change materials (PCMs) with high optical contrast. However, the on–off behavior of the phase change process results in the binary response of photonic devices, limiting the applications to the two-stage modulation. In this work, we propose a reconfigurable metasurface emitter based on a gold nanorod array on a VO2 thin film for achieving continuously tunable narrowband thermal emission. The electrode line connecting the center of each nanorod not only enables emission excitation electrically but also activates the phase transition of VO2 beneath the array layer due to Joule heating. The change in the dielectric environment due to the VO2 phase transition results in the modulation of emissivity from the plasmonic metasurfaces. The device performances regarding critical geometrical parameters are analyzed based on a fully coupled electro-thermo-optical finite element model. This new metasurface structure extends the binary nature of PCM based modulations to continuous reconfigurability and provides new possibilities toward smart metasurface emitters, reflectors, and other nanophotonic devices. 

Metasurfaces consisting of an array of planar sub-wavelength structures have shown great potentials in controlling thermal infrared radiation, including intensity, coherence, and polarization. These capabilities together with the two-dimensional nature make thermal metasurfaces an ultracompact multifunctional platform for infrared light manipulation. Integrating the functionalities, such as amplitude, phase (spectrum and directionality), and polarization, on a single metasurface offers fascinating device responses. However, it remains a significant challenge to concurrently optimize the optical, electrical, and thermal responses of a thermal metasurface in a small footprint. In this work, we develop a center-contacted electrode line design for a thermal infrared metasurface based on a gold nanorod array, which allows local Joule heating to electrically excite the emission without undermining the localized surface plasmonic resonance. The narrowband emission of thermal metasurfaces and their robustness against temperature nonuniformity demonstrated in this work have important implications for the applications in infrared imaging, sensing, and energy harvesting. 

Abstract Thermal interfaces are vital for effective thermal management in modern electronics, especially in the emerging fields of flexible electronics and soft robotics that impose requirements for interface materials to be soft and flexible in addition to having high thermal performance. Here, a novel sandwich‐structured thermal interface material (TIM) is developed that simultaneously possesses record‐low thermal resistance and high flexibility. Frequency‐domain thermoreflectance (FDTR) is employed to investigate the overall thermal performance of the sandwich structure. As the core of this sandwich, a vertically aligned copper nanowire (CuNW) array preserves its high intrinsic thermal conductivity, which is further enhanced by 60% via a thick 3D graphene (3DG) coating. The thin copper layers on the top and bottom play the critical roles in protecting the nanowires during device assembly. Through the bottom‐up fabrication process, excellent contacts between the graphene‐coated CuNWs and the top/bottom layer are realized, leading to minimal interfacial resistance. In total, the thermal resistance of the sandwich is determined as low as ~0.23 mm² K W⁻¹. This work investigates a new generation of flexible thermal interface materials with an ultralow thermal resistance, which therefore renders the great promise for advanced thermal management in a wide variety of electronics.