Simultaneous and independent manipulation of light’s propagation direction, polarization state, and wavelength remains a fundamental challenge in photonics, due to the intrinsic entanglement of optical degrees of freedom imposed by reciprocity and structural symmetry. Here, we present a single-layer dielectric Möbius metasurface that achieves fully decoupled control across these three dimensions by leveraging a topology-inspired polarization-path inversion mechanism. Inspired by Möbius topology, our design maps forward and backward polarization trajectories onto a unified Poincaré sphere via a synthetic phase-driven coordinate transformation, enabling direction-selective phase responses for arbitrary elliptical polarization states. To overcome the trade-offs between dispersion and polarization functionality, we introduce a neural network framework that co-optimizes Jones matrix responses across multiple polarizations, wavelengths, and directions. Experimentally, we demonstrate six completely independent holographic channels—defined by three polarization–wavelength combinations under opposite propagation directions—with high-fidelity image reconstructions and inter-channel crosstalk below 6.4%. In contrast to Janus-type or multilayer metasurfaces limited to interleaved or orthogonal polarization encoding, our approach offers a compact, lossless, and fabrication-compatible solution for multidimensional optical multiplexing.

The ultrafast and large-contrast switching of light is essential to the realization of high-speed, energy-efficient optical logic elements and sources. Such functionality requires optical materials or systems whose optical response can be rapidly and dramatically tuned under an external stimulus. However, achieving high-contrast switching, in sub-picosecond time scales, with low power over macroscopic length scales, is exceedingly difficult. We utilize self-assembled, cavity-coupled tin-doped indium oxide nanocrystal monolayers to achieve sub-picosecond, high-contrast switching across the mid-infrared (from 2.5 to 6.1 μm). We achieve reflection modulation up to 40% absolute and 1200% relative depth, under moderate fluences of a few hundred μJ/cm2, whereas our pump-probe experiments reveal an upper bound on response times of 210 femtoseconds. The strong and ultrafast nonlinearity, along with the broad spectral tunability and scalable fabrication method, make the demonstrated system an appealing platform for a range of mid-infrared applications, including ultrafast optical switching and mode-locked lasers.

Microbial infections, particularly those caused by emerging and antibiotic-resistant pathogens pose grave threats to human health. As a powerful antibiotic-free strategy, light-triggered therapy offers non-invasive treatment with low side effects, broad antimicrobial spectra, and reduced resistance potency. Among various light-responsive antimicrobial agents, fluorescent cationic polyelectrolytes (FCPs) have attracted great attention due to their intrinsic dark toxicity to microbes together with efficient generation capabilities of reactive oxygen species and heat under light irradiation, enabling multifaceted antimicrobial treatment via photodynamic and/or photothermal therapies. This review summarizes the recent advances in the synthesis and light-triggered antimicrobial applications of different types of FCPs, including side-chain fluorescent cationic polyelectrolytes (SFCPs) and main-chain fluorescent cationic polyelectrolytes (MFCPs). The commonly used synthetic routes and structures of SFCPs and MFCPs are discussed in detail. In view of the critical role of positively charged moieties, we further classify FCPs into different groups based on their embedded cationic structures and provide a detailed description of the light-triggered antimicrobial scenarios of SFCPs and MFCPs bearing different cations. Finally, the existing challenges and future perspectives of FCP-based antimicrobial phototherapy are outlined to provide insights into the development of FCP bactericides with more diversified structures and advanced functionalities.

Erbium-doped/erbium-ytterbium co-doped waveguide amplifiers (EDWAs/EYCDWAs) have received much attention as essential components within large-scale functionalized silicon-based optoelectronic (SBO) chips for their remarkable ability to amplify optical signals on-chip at the communication band combined with their potential application across diverse fields. We reviewed the research progress of EDWAs/EYCDWAs comprehensively. In particular, the research advancements concerning amplifiers constructed with diverse host materials are introduced in detail, and the gain limitations of the waveguide amplifiers are thoroughly analyzed from multiple perspectives, such as host materials and innovative structural designs. Subsequently, the preparation processes of the gain medium and waveguide structure in EDWAs/EYCDWAs are discussed, and their common application scenarios and commercial applications are summarized. In addition, an assessment is carried out on the challenges encountered by EDWAs/EYCDWAs. Finally, a discussion is held on their potential applications and development prospects in the field of SBO chips, with the aspiration of providing valuable references for the development of EDWAs/EYCDWAs.

Integrated photonics has transformed optical technology, yet conventional on-chip waveguides remain constrained to planar geometries with limited design flexibility.At the same time, applications spanning chiral sensing, quantum optics, nonlinear optics, and lab-on-chip spectroscopy require more versatile waveguide platforms for strong light-matter interaction.In this issue, researchers introduce the concept of the twisted hollowcore light cage, a chiral on-chip waveguide platform with an air core fabricated via 3D nanoprinting.These sidewise-open structures leave the air core accessible to external species while their built-in twist imparts a strong chiral response, achieving twist rates and circular dichroism over two orders of magnitude higher than in twisted hollow-core fibers.The cover of Advanced Photonics Volume 7, Issue 4, features a schematic of the chiral waveguide transmitting one circular polarization.By uniting hollow-core guidance, lateral accessibility, and structural chirality, twisted light cages offer functionalities that surpass those of conventional on-chip waveguides and twisted fibers, establishing a new building block for integrated chiral photonics.The image is based on the research presented in the article by

Robust three-dimensional (3D) recognition across different viewing angles is crucial for dynamic applications such as autonomous navigation and augmented reality; however, the application of the technology remains challenging owing to factors such as orientation, deformation, and noise. Wave-based analogous computing, particularly diffraction neural networks (DNNs), constitutes a scan-free, energy-efficient means of mitigating these issues with strong resilience to environmental disturbances. Herein, we present a real-time all-directional 3D object recognition and distortion correction system using a deep knowledge prior DNN. Our approach effectively addressed complex two-dimensional (2D) and 3D distortions by optimizing the metasurface parameters with minimal training data and refining them using DNNs. Experimental results demonstrate that the system can effectively rectify distortions and recognize objects in real time, even under varying perspectives and multiple complex distortions. In 3D recognition, the prior DNN reliably identifies both dynamic and static objects, maintaining stable performance despite arbitrary orientation changes, highlighting its adaptability to complex and dynamic environments. Our system can function either as a preprocessing tool for imaging platforms or as a stand-alone solution, facilitating 3D recognition tasks such as motion sensing and facial recognition. It offers a scalable solution for high-speed recognition tasks in dynamic and resource-constrained applications.

All-inorganic CsPbBr3 perovskite polycrystalline films, renowned for their remarkable optoelectronic properties, solution processability, and enhanced stability over organic–inorganic counterparts, are emerging as next-generation gain media for high-performance lasers. However, due to the limited understanding of how to realize population inversion under slow carrier injection, and a lack of convenient strategies to suppress Auger recombination while retaining low optical loss, achieving high-performance quasi-continuous-wave (quasi-CW) or CW lasing based on CsPbBr3 films at ambient temperature is still challenging. We devised a phase reconstruction strategy employing volatile ammonium, which achieves substantial suppression of Auger recombination through elimination of low-dimensional phase impurities and remains low optical loss via precisely controlled film crystallization dynamics. Importantly, this strategy emphasizes the critical role of Auger recombination suppression for high-performance lasing under slower carrier injection. Ultimately, an ultralow amplified spontaneous emission threshold of 9.6 μJ cm−2 was achieved under quasi-continuous nanosecond-pulsed excitation, which facilitated the realization of a single-mode vertical-cavity surface-emitting laser with a threshold of 17.3 μJ cm−2 and a quality factor of 3850 under quasi-CW pumping. We represent the exceptional performance of quasi-CW lasing to date, offering valuable insights for future advancements in high-performance CW lasing and even electrically driven lasers.