Metasurface-based imaging has attracted considerable attention owing to its compactness, multifunctionality, and subwavelength coding capability. With the integration of computational imaging techniques, researchers have actively explored the extended capabilities of metasurfaces, enabling a wide range of imaging methods. We present an overview of the recent progress in metasurface-based imaging techniques, focusing on the perspective of computational imaging. Specifically, we categorize and review existing metasurface-based imaging into three main groups, including (i) conventional metasurface design employing canonical methods, (ii) computation introduced independently in either the imaging process or postprocessing, and (iii) an end-to-end computation-optimized imaging system based upon metasurfaces. We highlight the advantages and challenges associated with each computational metasurface-based imaging technique and discuss the potential and future prospects of the computational boosted metaimager.

Interfacial solar steam generation (ISSG) is a novel and potential solution to global freshwater crisis. Here, based on a facile sol-gel fabrication process, we demonstrate a highly scalable Janus aramid nanofiber aerogel (JANA) as a high-efficiency ISSG device. JANA performs near-perfect broadband optical absorption, rapid photothermal conversion and effective water transportation. Owning to these features, efficient desalination of salty water and purification of municipal sewage are successfully demonstrated using JANA. In addition, benefiting from the mechanical property and chemical stability of constituent aramid nanofibers, JANA not only possesses outstanding flexibility and fire-resistance properties, but its solar steaming efficiency is also free from the influences of elastic deformations and fire treatments. We envision JANA provides a promising platform for mass-production of high-efficiency ISSG devices with supplementary capabilities of convenient transportation and long-term storage, which could further promote the realistic applications of ISSG technology.

High-dimensional entanglement is of great importance in quantum communications and can be realized by encoding information on multiple degrees of freedom (DoFs) of the photons. Conventionally, the realization of such high-dimensional entanglement involves different combinations of bulky optical elements. In this work, we present the use of a single dielectric metasurface to generate high-dimensional entanglement by modulating multi-DoFs of photons. By sending one of the polarization-entangled photons to interact with the metasurface, we encode path, spin angular momentum, and orbital angular momentum information to the original state. We achieve a four-qubit quantum state in the experiment. To verify it, we experimentally demonstrate the nonlocal correlations between the two photons by recording the correlated images, and we also perform a quantum state tomography measurement. This scheme can be applied to on-chip quantum state manipulation, which is promising in quantum communication with integrated components.

Achromatic metalens composed of arrays of subwavelength nanostructures with spatially varying geometries is attractive for a number of optical applications. However, the limited degree of freedom in the single layer achromatic metasurface design makes it difficult to simultaneously guarantee the sufficient phase dispersion and high diffraction efficiency, which restricts the achromatic bandwidth and efficiency of metalens. Here we propose and demonstrate a high efficiency achromatic metalens with diffraction-limited focusing capability at the wavelength ranging from 1000 nm to 1700 nm. The metalens comprises two stacked nanopillar metasurfaces, by which the required focusing phase and dispersion compensation can be controlled independently. As a result, in addition to the large achromatic bandwidth, the averaged focusing efficiency of the bilayer metalens is higher than 64% at the near-infrared region. Our design opens up the possibility to obtain the required phase dispersion and efficiency simultaneously, which is of great significance to design broadband metasurface-based optical devices.Achromatic metalens composed of arrays of subwavelength nanostructures with spatially varying geometries is attractive for a number of optical applications. However, the limited degree of freedom in the single layer achromatic metasurface design makes it difficult to simultaneously guarantee the sufficient phase dispersion and high diffraction efficiency, which restricts the achromatic bandwidth and efficiency of metalens. Here we propose and demonstrate a high efficiency achromatic metalens with diffraction-limited focusing capability at the wavelength ranging from 1000 nm to 1700 nm. The metalens comprises two stacked nanopillar metasurfaces, by which the required focusing phase and dispersion compensation can be controlled independently. As a result, in addition to the large achromatic bandwidth, the averaged focusing efficiency of the bilayer metalens is higher than 64% at the near-infrared region. Our design opens up the possibility to obtain the required phase dispersion and efficiency simultaneously, which is of great significance to design broadband metasurface-based optical devices.