Optically transparent, broadband and omnidirectional microwave absorber based on graphene-SiO metasurfaces.

Broadband and omnidirectional absorption of electromagnetic waves is required in various technologies, such as stealth, high quality wireless communications, spacecraft shielding. In this study, we theoretically and numerically study a graphene-based absorber achieving broadband and omnidirectional absorption from 4 GHz to 100 GHz and 0 to 50 ∼70 , with over 90% absorption efficiency. By applying a thin layer of graphene upon a SiO moth-eye structure, we show that electromagnetic waves can be effectively absorbed in the graphene layer and that the structure is optically transparent, ideal for civilian and military applications.

High-Index Dielectric Metasurfaces Performing Mathematical Operations.

Image processing and edge detection are at the core of several newly emerging technologies, such as augmented reality, autonomous driving, and more generally object recognition. Image processing is typically performed digitally using integrated electronic circuits and algorithms, implying fundamental size and speed limitations, as well as significant power needs. On the other hand, it can also be performed in a low-power analog fashion using Fourier optics, requiring, however, bulky optical components.

Structural coloration with hourglass-shaped vertical silicon nanopillar arrays.

We demonstrate that arrays of hourglass-shaped nanopillars patterned into crystalline silicon substrates exhibit vibrant, highly controllable reflective structural coloration. Unlike structures with uniform sidewall profiles, the hourglass profile defines two separate regions on the pillar: a head and a body. The head acts as a suspended Mie resonator and is responsible for resonant reflectance, while the body acts to suppress broadband reflections from the surface.

Nonlocal Metasurfaces for Optical Signal Processing.

Optical analog signal processing has been gaining significant attention as a way to overcome the speed and energy limitations of digital techniques. Metasurfaces offer a promising avenue towards this goal due to their efficient manipulation of optical signals over deeply subwavelength volumes. To date, metasurfaces have been proposed to transform signals in the spatial domain, e.

Enhanced Photoresponse in Metasurface-Integrated Organic Photodetectors.

In this work, we experimentally demonstrate metasurface-enhanced photoresponse in organic photodetectors. We have designed and integrated a metasurface with broadband functionality into an organic photodetector, with the goal of significantly increasing the absorption of light and generated photocurrent from 560 up to 690 nm. We discuss how the metasurface can be integrated with the fabrication of an organic photodiode.