With the merits of non-contact, highly efficient, and parallel computing, optoelectronic synaptic devices combining sensing and memory in a single unit are promising for constructing neuromorphic computing and artificial visual chip. Based on this, a N:ZnO/MoS₂-heterostructured flexible optoelectronic synaptic device is developed in this work, and its capability in mimicking the synaptic behaviors is systemically investigated under the electrical and light signals. Versatile synaptic functions, including synaptic plasticity, long-term/short-term memory, and learning-forgetting-relearning property, have been achieved in this synaptic device. Further, an artificial visual memory system integrating sense and memory is emulated with the device array, and the visual memory behavior can be regulated by varying the light parameters. Moreover, the optoelectronic co-modulation behavior is verified by applying mixed electric and light signals to the array. In detail, a transient recovery property is discovered when the electric signals are applied in synergy during the decay of the light response, of which property facilitates the development of robust artificial visual systems. Furthermore, by superimposing electrical signals during the light response process, a differentiated response of the array is achieved, which can be used as a proof of concept for the color perception of the artificial visual system.

The remarkable capability in regulating light polarization or amplitude at the nanoscale makes metasurface a leading candidate in high‐resolution image display and optical encryption. Diverse binary or grayscale meta‐images were previously shown concealed in a single metasurface, yet they are mostly stored at same encryption level and share an identical decryption key, running the risk of exposing all images once the key is disclosed. Here, we propose a twofold optical display and encryption scheme demonstrating that binary and grayscale meta‐images can be concurrently embedded in a nonspatially multiplexed silicon metasurface, and their decryptions demand for drastically different keys. Unlike previous metasurfaces relying on isolated transmission or phase manipulations upon orthogonal linear polarization incidences, this is made possible by exploiting silicon meta‐atoms featuring joint transmission amplitude and polarization control at two wavelengths. In detail, the selected two meta‐atoms exhibit large polarization‐independent transmission difference (∼85 %) at a wavelength of 800 nm, while functioning as the nano‐quarter‐wave plate at wavelength of 1200 nm. Through elaborate design in simulation, a binary image can be witnessed when the metasurface is merely illuminated by an unpolarized light of wavelength 800 nm or under white light illumination. However, a distinct binary or grayscale image will come into view by inspecting the metasurface with an analyzer and when the incident light is circularly polarized at the wavelength of 1200 nm. Two metasurface samples are fabricated and successfully verified the claims experimentally. The proposed approach is expected to bring new insights to the field of optical display and encryption.

As a prominent alternative to toxic dyes/pigments, nanostructural color pixels have garnered tremendous attention in applications related to display/imaging devices and color printings. However, current color pixels mostly offer static color responses. In relation to this, dynamic color tuning properties must be investigated in order to expand their functionalities and promote their use in the fields of encryption and anti‐counterfeiting. In this study, a simple array of hydrogenated amorphous silicon nanogratings is proposed to realize polarization‐encrypted full‐color images via the coupling of incident light into different leaky mode resonances within the nanogratings. The proposed pixels can readily switch from vivid full colors to indistinguishable orange color by altering the incident polarization state. Hence, unlike the reported polarization‐tuned color generation schemes that merely allow for the color variation of the image or require complicated designs to hide the color information, the proposed approach can encrypt arbitrary full‐color images via a simple tuning of the incident polarization state. Owing to the localized leaky mode resonances supported by the nanogratings, the pixel can still implement the polarization‐encrypted functionality even when it contains only four gratings, thus enabling a remarkably high resolution. The proposed simple scheme may provide a credible new pathway for accelerating the practical applications of high‐resolution encryption and anti‐counterfeiting.

The increase in the number of people suffering diabetes has been the driving force behind the development of glucose sensors to overcome the current testing shortcomings. In this work, a reusable, non-invasive and ultrafast radio frequency biosensor based on optimized integrated passive device fabrication process for quantitative detection of glucose level was developed. With the aid of the novel biosensor design with hammer-shaped capacitors for carrying out detection, both the resonance frequency and magnitude of reflection coefficient can be applied to map the different glucose levels. Meanwhile, the corresponding fabrication process was developed, providing an approach for achieving quantitative detection and a structure without metal-insulator-metal type capacitor that realizes low cost and high reliability. To enhance the sensitivity of biosensor, a 3-min dry etching treatment based on chlorine/argon-based plasma was implemented for realizing hydrophilicity of capacitor surface to ensure that the biosensor can be touched rapidly with glucose. Based on above implementation, a non-invasive biosensor having an ultrafast response time of superior to 0.85 s, ultralow LOD of 8.01 mg/dL and excellent reusability verified through five sets of measurements are realized. The proposed approaches are not limited the development of a stable and accurate platform for the detection of glucose levels but also presents a scheme toward the detection of glucose levels in human serum.

Silicon dielectric metasurfaces based on a square lattice of nanoparticles have been extensively utilized to create transmissive structural colors. Yet it is a huge challenge to obtain stable yellow color with high saturation due to the relatively large absorption of silicon in the short wavelength regime and the applied square lattice. In this study, we propose a new design strategy of independently altering the mutually perpendicular periods of a hydrogenated amorphous silicon nanodisk array-enabled metasurface to meticulously modulate the transmission spectra for the realization of high-saturation and stable cyan, magenta and yellow (CMY) color pixels. By introducing rectangular lattice, the yellow pixel can provide a narrowband transmission spectrum with a highly suppressed dip at 455 nm. The high suppression in transmission contributes to give rise to high-saturation yellow color. The attained narrowband spectrum that enables low spectral cross-talk is attributed to the overlap between magnetic dipole resonance excited by individual nanodisks and lattice resonance arising from the dipole coupling between the nanodisks. Compared with the square lattice, the proposed pixels exhibit fairly stable output color responses for a large period range. Meanwhile, the proposed CMY pixels are capable of both the relaxed angular tolerance and low dependence on the incident polarization states. It is anticipated that the proposed color pixels pave the way for extensive applications in compact color displays.