Highly efficient and ultra-broadband graphene oxide ultrathin lenses with three-dimensional subwavelength focusing
Nanometric flat lenses with three-dimensional subwavelength focusing are indispensable in miniaturized optical systems. However, they are fundamentally challenging to achieve because of the difficulties in accurately controlling the optical wavefront by a film with nanometric thickness. Based on the unique and giant refractive index and absorption modulations of the sprayable graphene oxide thin film during […]
Free-standing graphene oxide mid-infrared polarizers
Mid-infrared (MIR) represents crucial spectral region for applications in spectroscopy, sensing, imaging, security and industry screening, owing to the strong characteristic vibrational transitions of many important molecules. However, the current MIR compatible materials are fragile, hazardous, and costly, which hampers the performance of MIR devices. Here, we developed a versatile transmittance-based Kramers-Kronig method and obtained […]
Structured graphene metamaterial selective absorbers for high efficiency and omnidirectional solar thermal energy conversion
An ideal solar-thermal absorber requires efficient selective absorption with a tunable bandwidth, excellent thermal conductivity and stability, and a simple structure for effective solar thermal energy conversion. Despite various solar absorbers having been demonstrated, these conditions are challenging to achieve simultaneously using conventional materials and structures. Here, we propose and demonstrate three-dimensional structured graphene metamaterial […]
A 90-nm-thick graphene metamaterial for strong and extremely broadband absorption of unpolarized light
Broadband strong light absorption of unpolarized light over a wide range of angles in a large-area ultrathin film is critical for applications such as photovoltaics, photodetectors, thermal emitters and optical modulators. Despite long-standing efforts in design and fabrication, it has been challenging to achieve all these desired properties simultaneously. We experimentally demonstrate a 12.5 cm2, […]
