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High performance broadband absorbers in the midinfrared atmospheric transparency windows are of great importance in various applications, such as energy harvesting, photodetection, radiative cooling, and stray light elimination. In recent years, great efforts have been made to develop absorbers using plasmonic nanostructured resonators in the infrared regime. Although these approaches promise distinct advantages in performance enhancement, they still suffer several obstacles, e.g., limitations on sample size, bandwidth, and fabrication throughput. Here, a large‐area broadband wide‐angle plasmonic metasurface absorber with nearly perfect absorption over the range of midwavelength infrared atmospheric transparent window (3–6 µm) is proposed and experimentally demonstrated. The metasurface absorber is basically comprised of a monolayer of sub‐micrometer‐sized polystyrene spheres self‐assembled on an opaque metallic substrate and coated with metal–insulator–metal three‐layer thin film, and fabricated by using simple, low‐cost self‐assembly techniques. Numerical simulation analyses not only corroborate the experimental observations, but also discover that such broadband absorption effect is attributed to hybrid plasmonic multiple resonances. The combination of the significant light absorption effect, compact design, and high‐yield self‐assembly fabrication process suggests that the proposed absorber has wide prospect application in integrated optical and optoelectronic systems.

We employed both theoretical calculations and experiments to study the nonlinear responses in optical metamaterials. The spectra of second-harmonic generations measured on a fishnet metamaterial are in quantitative agreements with calculations based on full-wave numerical simulations combined with field integrations, both exhibiting ~80 times enhancements at the magnetic resonance frequency. Our calculations explained several interesting features observed experimentally, and suggested an optimal metamaterial structure to yield the strongest nonlinear signals.

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The development of novel approaches that control absorption and emission operating in long wavelength infrared (LWIR) spectral region is of fundamental importance for many applications, such as, remote temperature sensing, environmental monitoring, thermal imaging, radiation cooling and industrial facility inspections. A high performance plasmonic metasurface-based absorber for the LWIR spectral region is presented. In our design, a pyroelectric thin film, poly(vinylidene fluoridetrifluoroethylene) (P(VDF-TrFE)) copolymer, is introduced as spacer, that offers the device not only with multiple selective high absorption bands but also promising potential for application in optoelectronics. By employing a scattering-type near-field optical microscopy (s-SNOM), both the near-field amplitude and phase optical responses of the absorber are investigated at resonant wavelength, thereby providing direct experimental evidence to verify the nature of the absorption effect. To further demonstrate the versatility of our design, a particular metasurface patterned by the building blocks of the plasmonic absorber is fabricated and characterized. Two-dimensional hyperspectral images show that such a patterned structure exhibits both frequency and spatially selective absorption.

In this work, the authors propose and experimentally demonstrate a large-area long-wavelength infrared thermal emitter, which is spectrally selective, highly directional, and easily fabricated.

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