Lina Shi

Plasmonic metasurfaces can achieve static structural colors with high resolution, high efficiency, high saturation, and a wide color gamut. Integrating phase change materials and electro-optical components into metasurfaces can further achieve dynamically adjustable structural colors. However, it remains challenging to build a platform with independent control of the basic structural color attributes [HSB (hue, saturation, and brightness)] and dynamic polarization response. Here, we demonstrate a plasmonic metasurface based on an anisotropic Al nanopillar array and achieve independent control over the hue, saturation, and brightness of the structural colors through the geometric parameters of the nanopillar array. It is also shown that dynamic color adjustability can be achieved by adjusting the angles of the polarizer and the analyzer. Our scheme provides a simple method for achieving three-dimensional HSB color control and polarization-driven dynamic response in structural colors. This greatly enhances the information capacity and flexibility of optical metasurfaces in fields such as high-density displays and optical encryption.

Angular momentum (AM) holography encodes information onto a single metasurface, encompassing both the spin and orbital AM dimensions of light, providing a high-dimensional space for optical encryption. However, the trade-off between the ever-increasing channel multiplexing capacity and the computational cost of generating the required phase distribution in real time limits existing AM encryption schemes to static, offline-designed architectures with fixed key mappings. This paper proposes a Dynamic AM Holographic Encryption (DAHE) framework that co-designs fast phase synthesis and time-varying key derivation on a non-interlaced metasurface platform. The dual-domain wavelet attention network generates the basic phase hologram in approximately 221 ms per channel on a single Graphics Processing Unit, while the Transformer-based module derives a non-repeating optical key set from a timestamped user identifier within 5 ms. Both outputs are fed into a deterministic overlay layer where we propose a comb-convolutional spiral phase encoding strategy. By convolving the spiral phase with a two-dimensional Dirac comb function, the orbital AM singularity is replicated on a periodic local central lattice, thereby achieving efficient multi-channel AM multiplexing across the entire monolithic metasurface and producing the final multiplexed metasurface phase. Multi-user time-varying access experiments confirm that correct image reconstruction requires valid user identity, timestamps, and matching AM optical states simultaneously; unauthorized or time-mismatched queries only return noise. The DAHE framework combines real-time holographic phase engineering with updatable cryptographic key management, opening a practical pathway for dynamic secure displays and optical authentication.

Structural colors have always attracted much attention due to important applications in display devices, imaging security certification, optical data storage, and so on. The brightness of structure colors, as the carrier of chiaroscuro information, is the key to making images appear stronger in the spatial and three-dimensional sense. However, relatively little work has been done on the control of the color brightness, and the reported structures are complex and difficult to fabricate. Here, we demonstrate a low-aspect-ratio anisotropic metasurface consisting of a PMMA film patterned by arrays of elliptical-shaped holes clamped by two thin aluminum films. By utilizing localized surface plasmon resonances, we realize a three-dimensional (3D) HSB (hue, saturation, and brightness) structure color with independent brightness control and enhance the cross-polarization reflection, covering approximately 120% of the sRGB color gamut. It is shown that the ratio of the major and minor axes leads to the independent control of brightness of the structural colors. The nanoprinting of HSB images with smooth brightness transitions is demonstrated through elaborate design of the metasurface geometry parameters and CMOS-compatible micro–nano fabrication process. Our findings will facilitate the broad range of 3D nanoprinting and modern advanced display applications.

Extreme ultraviolet (EUV) light with a 13.5 nm wavelength plays a crucial role in many fields, such as microelectronics manufacturing and material science. However, conventional transmissive meta-optics designs for EUV light face great challenges due to the strong absorption of most materials and the near-unity real part of the refractive indices, which usually prevent waveguiding and effective refraction. Here, we numerically demonstrate the focusing of EUV light at 13.5 nm by the elaborately designed molybdenum (Mo) metalens based on the nanohole array. Compared with other candidate materials, Mo-based metalens sustains efficient propagation of the 13.5 nm EUV light through nanoholes milled on the membrane, leading to the focal spot with a diffraction-limited size of 46 nm and a focusing efficiency of 27.8%. In addition, the dependence of the focusing efficiency on the self-supporting Si or Si3N4 membrane is investigated. The proposed Mo-based metalens for the focusing of the 13.5 nm EUV light holds promising applications in semiconductor lithography, high-resolution imaging, and ultrafast spectroscopy.

Bound states in the continuum (BICs) with extremely large quality factors (Q factors) can enhance the light–matter interaction and thus achieve low-threshold lasing. Here, we theoretically propose and experimentally demonstrate the low-threshold lasing at room temperature based on BICs. A threshold of approximately 306.7 W/cm² (peak intensity) under a 7.5 ns-pulsed optical excitation is presented in an all-dielectric metasurface system consisting of titanium dioxide (TiO₂) nanopillars with a dye film. Also, the multimode lasing can be excited by the higher pumping. Our results may find exciting applications in on-chip coherent light sources, filtering, and sensing.

Structural colorations with all-dielectric metasurfaces provide a dye-free approach for integrated sub-wavelength color generation with enhanced stability and environmental friendliness. However, it remains challenging to simultaneously tailor all the elementary color functions, hue, saturation, and brightness, in a simple platform. Here, we report a generic principle to create bright-field full-color nanoprinting with brightness control by using all-dielectric metasurfaces consisting of arrays of Si elliptical nanopillars. It is demonstrated that the lower order Mie resonances in the reflection spectra redshift with the sizes of the elliptical nanopillars when the incident light polarization is fixed along the major or minor axes. By designing the structure carefully, basic colors, such as red, green, blue, and yellow, are obtained across the visible spectrum. Experimental measurements show that the fabricated colors are independent with respect to the viewing angle owing to the Mie resonance origin. Moreover, we demonstrate that, by varying the angle of either the polarizer or the analyzer, the resonant wavelengths keep invariant while the reflection intensity decreases, leading to the tuning of the brightness of colors from bright to dark without changing the hue and saturation. Our scheme provides a simple yet general approach for the full hue, saturation, brightness control of structural colors, holding great potential in diverse applications, such as anti-counterfeiting technologies, 3D displays, and information storage.