Infrared imaging is indispensable for its ability to penetrate obscurants and visualize thermal signatures, yet its practical use is hindered by the intrinsic limitations of conventional detectors. Nonlinear upconversion, which converts infrared light into the visible band, offers a promising pathway to address these challenges. Here, we demonstrate high-efficiency infrared upconversion imaging using nonlinear silicon metasurfaces. By strategically breaking in-plane symmetry, the metasurface supports a high-Q quasi-bound states in the continuum resonance, leading to strongly enhanced third-harmonic generation (THG) with a conversion efficiency of 3×10⁻⁵ at a pump intensity of 10 GW/cm². Through this THG process, the metasurface enables high-fidelity upconversion of arbitrary infrared images into the visible range, achieving a spatial resolution of ~6 μm as verified using a resolution target and various customized patterns. This work establishes a robust platform for efficient nonlinear conversion and imaging, highlighting the potential of CMOS-compatible silicon metasurfaces for high-performance infrared sensing applications with reduced system complexity.

In video conferencing and facial recognition applications, eyeglass reflection often obscures critical facial features. Polarization information helps disentangle reflection and transmission components. Existing polarization reflection removal approaches rely on large-scale paired polarization datasets, making them hard to generalize to the scenes under unseen lighting conditions. To address these challenges, we propose PDPrior, an untrained polarization-guided diffusion prior for eyeglass reflection removal. The PDPrior requires no training data, and no ground-truth reflection-free images. It operates solely on polarization observations collected at test time to achieve artifact-free, high-fidelity reflection removal. The PDPrior leverages the generative prior of a diffusion model and introduces polarization as guidance to control the generation process. The self-supervised loss based on the forward model is employed to alternately update the reflection and transmission variables, endowing the generative model with physical interpretability. Extensive experimental results validate the effectiveness and robustness of the method on eyeglass reflection data captured in both indoor and outdoor lighting conditions, achieving higher face image quality assessment scores for recognition performance compared to state-of-the-art methods.

Scene-level high-precision 3D imaging remians a key challenge due to the trade-offs between imaging distance and accuracy. While polarization-based 3D imaging offers potential, it offen fails facing "discontinuous" targets—environments where multiple objects are separated by space resulting from surface normal integration. A recent work integrating binocular stereo vision with polarization information successfully recovers depth by iteration. This intergation-free appoach paves the way for scene-level high-precision 3D imaging and future applications.

Compound eyes (CEs) offer a unique design paradigm for developing artificial micro-optical systems. However, current bionic CEs still fall significantly short of their insect counterparts in performance, particularly regarding ommatidial spatial arrangement, size distribution, visual field adaptability and environmental perception. Inspired by the CEs of Sympetrum frequens, we developed a tunable bionic CE with bi-focal ommatidia by integrating a flexible lens-on-lens (LoL) array with microfluidics, enabling simultaneous bi-focal imaging. The polydimethylsiloxane (PDMS) LoL array was fabricated through sequential processing steps, including femtosecond laser dual-modification of quartz glass, two-step wet etching, and soft lithography using the resulting glass template. Integration of this flexible LoL array with a microfluidic chip produced a tunable CE with bi-focal ommatidia, allowing liquid-pressure modulation of CE configurations. We systematically investigated the optical performance of both LoL ommatidia and the integrated CE, including bi-focal focusing/imaging properties, tunable field-of-view (FOV), large-FOV imaging, and moving target monitoring. This tunable CE with LoL ommatidia demonstrates significant potential for cutting-edge applications.

Metasurface fabrication still faces critical processing challenges in balancing the structural order and disorder, achieving high-speed patterning, and extending material compatibility to refractory metals for operation under extreme conditions. This study demonstrates that femtosecond laser maskless direct writing (fs-LMDW) offers a versatile platform for engineering multispectral information, all-in-one metasurfaces on pure zirconium (Zr) substrates. Through sequential fs-LMDW in air and ethylene glycol (EG), deceptive grey-colored visible information is superimposedly encoded with the infrared (IR)-encrypted information (invisible among black-color structured background), which leverages the crosstalk-free structural modulation of singular-band IR and visible light. The metasurface exhibits robust thermal stability and high-security encryption capability across a wide temperature range, with IR-concealed information (such as QR code) remaining securely encrypted until thermally activated at 300 °C for smartphone-readable information decryption. Furthermore, the visible information is both erasable through 300 °C oxidation heating in air and rewritable via fs-LMDW in EG without compromising IR encryption security. Particularly, the one-time complete erasability makes it possible to identify whether the encrypted IR-information has been decrypted, underscoring the robustness and high security of the platform. The presented hierarchical micro/nanostructuring methodology is deemed to be applicable to a large material matrix to gain high-security, and multifunctional metasurfaces that are more difficult and complex for current metasurface fabrication techniques.

Bound states in the continuum (BICs) have emerged at the forefront of optics and nanophotonics due to their exceptionally high quality-factors and unique topological characteristics. Advances in design capabilities, nanofabrication and characterization have enabled precise control of BIC resonances at subwavelength scale, unlocking exciting opportunities for applications in diverse areas such as lasing, optical sensing and nonlinear optics. The integration of phase-change materials and liquid crystals has facilitated dynamic control over light emission and absorption. In this Review, we provide a comprehensive overview of the latest progress in BIC research, covering both foundational concepts and recent advances. We begin with the underlying physics and highlight emerging design strategies, including machine learning and inverse design approaches. We discuss major breakthroughs in super-BICs, chiral BICs, intriguing concepts of flatband BICs and Moiré BICs, along with exotic phenomena, such as strong light-matter interaction, ultrafast dynamics and exceptional points. We further review the recent advancements and key challenges in BIC-enabled applications. Finally, we offer our perspectives on the promising future of BIC in fundamental research emphasizing emerging directions such as multilayer metasurfaces, interfacing BICs with quantum emitters, new capabilities enabled by advanced fabrication and design, and pathways towards scalable integration into photonic BIC metadevices.

Conventional optical microscopy is fundamentally constrained by the optical diffraction limit (~200 nm), restricting the observation of nanoscale features in advanced manufacturing. To address this challenge, a remote-mode microsphere-enabled nanoscale imaging technology has been developed and successfully translated from laboratory innovation to industrial application. By utilizing a suspended transparent microsphere as a miniature lens, the system enables real-time, non-contact optical imaging and resolves 23 nm gaps on silicon wafers and 77 nm metal probes in hard-disk magnetic heads through reverse optical-path reconstruction of virtual images. The technology has been commercialized by PHAOS Technology, achieving over 300% annual sales growth and receiving the "Manufacturing Technology Disruptor of the Year" award. By integrating a universal lens adapter, the system allows a standard 20× objective to achieve imaging performance comparable to a 50× objective at only one-tenth of the cost of high-end super-resolution systems. This approach represents an important advancement in scalable and cost-effective nanometrology, providing a practical solution for real-time semiconductor inspection and industrial quality control.

Conventional terahertz (THz) single-pixel imaging relies on a sequential process involving compressed sensing, which requires a spatial modulator and is often time-intensive. Here, we propose a new THz single-pixel imaging scheme operating in a parallelized fashion with a pixelated metasurface, demonstrated within a standard THz time-domain spectroscopy system. This approach encodes spatial information through multiple narrow linewidth resonances based on bound states in the continuum (BIC) physics, and the BIC-enabled pixelated metasurface facilitates the near-field distributed sensing through local field enhancement. We validate this integrated imaging and sensing capability using a 2×2 metasurface array in a proof-of-concept experiment, with scalability to larger arrays. The approach achieves 100% accuracy in binary imaging reconstruction from a single THz pulse and enables refractive index sensing with a sensitivity higher than 14.39 GHz/RIU. Leveraging the intrinsic penetration capability of THz radiation, this technique offers significant promise for next-generation noninvasive applications such as security inspection and defect detection in semiconductor chips and pharmaceutical products.

Incorporating perovskite nanocrystals (PNCs) in the glass matrix has been demonstrated to be an effective route to improve their stability for long-term operation. However, simultaneously achieving high luminance and high photoluminescence (PL) quantum yield (QY) is challenging. Herein, we report a strategy that employs fluoride ion doping to modify the three-dimensional glass network, thereby optimizing the crystallization behavior of PNCs and achieving both high luminance and high PLQY in full-spectrum. Leveraging these high-performance transparent composites, we constructed a dynamic holographic multicolor display system by integrating with a spatial light modulator (SLM), achieving a pixel density as high as 20,247 pixels per inch (PPI). We further propose a vertically stacked, multilayer full-color display architecture that overcomes the limitations of color filters in light-utilization efficiency and the bottlenecks of conventional planar sub-pixel layouts in terms of spatial utilization and resolution.

Indium phosphide-based quantum dots (InP-based QDs) have emerged as promising candidates for next-generation display and optoelectronic technologies, offering exceptional photoluminescent (PL) properties including high efficiency, narrow emission spectra, and precisely tunable wavelengths. Nevertheless, their widespread commercialization encounters substantial obstacles, primarily stemming from persistent challenges in synthetic control and material processing. Critical performance parameters—including photoluminescence quantum yield (PL QY, currently<90% for most systems), emission linewidth (typically>35 nm) as well as external quantum efficiency (EQE) and operational stability of device—continue to show only incremental improvements, highlighting the urgent need for fundamental breakthroughs in QDs synthesis, surface engineering and device optimization. This review systematically examines the nucleation mechanisms governing InP core formation and outlines key strategies for optimizing InP-based core/shell QDs. Furthermore, we present a comprehensive analysis of recent breakthroughs in red, green, and blue-emitting InP-based QD light-emitting diodes (QLEDs) development, focusing on modulation of charge transport engineering and suppression of charge leakage. Finally, we critically evaluate the remaining commercialization challenges and future prospects for InP-based QLEDs in next-generation display and optoelectronic technologies, outlining potential pathways for overcoming current limitations.