Nontrivial nearfield topologies in nano-optics refer to nearfield configurations embedded within singularities or topological defects, providing an ideal platform to explore integrated optoelectronics and higher-dimensional topological physics. Exciting such field topologies relies on selection rules related to various conserved quantities. Unfortunately, existing algebraic rules focus primarily on scalar singularities in nano-optical (e.g., plasmonic) systems and largely neglect the vectorial nature of the fields. More critically, these rules remain phenomenological. Given the intrinsic link between conserved quantities and symmetries, here we establish a unified selection rule using group theory that govern the excitations of nontrivial field topologies across three photonic spin states in generic nanophotonic systems. This rule can act as building blocks for constructing selection rules for exciting and engineering higher-dimensional field topologies (embedded within vectorial singularities and quasiparticles). These rules are derived purely from symmetry arguments and are therefore rooted in first principles. The proposed rules further predict two novel physical effects in plasmonic systems: spin-orbit splitting of vortices and multidimensional nested vortices. Phase-resolved in-situ measurements of nested multidimensional plasmonic topologies well demonstrate our findings. Our group-theory-based approach can serve as a versatile framework for engineering symmetry- and singularity-related phenomena-like circular meron lattices and plasmonic quasicrystals-in diverse wave systems.

Nanobubbles are typical nanodefects commonly existing in two-dimensional (2D) van der Waals materials such as transition metal dichalcogenides, especially after their transfer from growth substrate to target substrates. These nanobubbles, though tiny, may significantly alter the local electric, optoelectronic, thermal, or mechanical properties of 2D materials and therefore are rather detrimental to the constructed devices. However, there is no post-processing method so far that can effectively eliminate nanobubbles in 2D materials after their fabrication and transfer, which has been a major obstacle in the development of 2D material based devices. Here, we propose a principle, called laser optothermal nanobomb (LOTB), that can effectively flatten nanobubbles in 2D materials through a dynamic process of optothermally induced phase transition and stress-pulling effect in nanobubbles. Operation of LOTB on monolayer molybdenum disulfide (1L-MoS2) films shows that the surface roughness can be reduced by more than 70% on a time scale of similar to 50 ms, without damage to the intrinsic property of 1L-MoS2 as validated by micro-nano photoluminescence and Raman spectroscopy. Moreover, a dual-beam cascaded LOTB and a multi-shot LOTB strategies are proposed to increase the flattened area and processing effect, showing the potential of LOTB for fast nanodefect repairing in the mass production of van der Waals materials and devices.

Objective Anti-reflection (AR) is a key technology for enhancing the performance of optical components and systems. The infrared band, which is minimally affected by atmospheric scattering, serves as a critical band for remote sensing and communications. Efficient infrared AR is essential for high-quality thermal imaging and other applications. For infrared anti-reflection, achieving high transmittance over a bandwidth of several micrometers is a major difficulty. Micro-nano structured anti-reflection technologies, represented by binary arrays and moth-eye structures, serve as primary solutions for broadband infrared anti-reflection, though their underlying physical priciples are fundamentally different. Researchers generally regard moth-eye structures as a preferred approach for achieving broadband antireflection. However, moth-eye structures exhibits strong height dependence-sufficient height is required to obtain excellent AR performance, which in turn increases fabrication difficulty and reduces mechanical stability. Binary arrays have also demonstrated broadband performance in the infrared band while exhibiting much lower height dependence. This indicates that binary arrays can maintain broadband AR properties with reduced fabrication complexity and enhanced mechanical robustness. Nevertheless, the physical origin of their weaker height dependence has not yet been thoroughly investigated. The broadband AR performance exhibited in shallow binary arrays has sparked interest in the realization pathway for ultra-broadband AR. This paper focuses on the essential requirements for ultra-broadband infrared anti-reflection, and deeply investigates the anti-reflection physical mechanisms of binary arrays and moth-eye structures by combining multiple electromagnetic field analysis methods to simulate light-micro/nano-structure coupling processes. The advantages and applicable regimes of binary arrays are revealed and the optimal pathway for realizing infrared ultra-broadband AR is clarified. Our work facilitates the design of ultra-broadband infrared AR devices and is of great significance for the development and application of infrared AR technology. Methods The finite-difference time-domain (FDTD) method, finite element method (FEM), and rigorous coupled-wave analysis (RCWA) are comprehensively employed to perform systematic simulations ranging from mode analysis and optical field manipulation to macroscopic optical performance. FDTD is used to calculate electric field distributions within the binary array and the moth-eye structure on the zinc sulfide (ZnS) surface. FEM is employed to simulate effective modes and corresponding effective refractive indices within the binary array, from which the phase shift and transmittance during light propagation are obtained. Based on simulation results and theoretical analyses, the optical impedance matching processes of both structures are elucidated. RCWA is utilized to compute the reflectance, transmittance and phase shift inside the binary array, serving as a cross-validation of FEM results and clarifying the physical mechanism as well as applicable regimes underlying the broadband AR performance of the binary array. Design of the binary array is also driven by RCWA and effects of duty ratio, height and incident angle are analyzed. Circular hole arrays are fabricated on the ZnS surface by semiconductor processes with two-step pattern transfer. The transmittance of the fabricated structures is characterized by Fourier transform infrared spectroscopy (FTIR), and their morphology is examined by scanning electron microscopy (SEM). Results and Discussions By analyzing the optical impedance matching processes of moth-eye structures and binary arrays, this paper reveals that binary arrays allow for instantaneous phase matching upon light incidence at the surface (Fig. 3), effectively removing reliance on structural height for AR performance. Furthermore, the physical mechanism underlying the broadband AR of binary arrays is elucidated, along with the wavelength band and height prerequisites required for realizing broadband performance (Fig. 4). The analysis integrates multiple electromagnetic field simulation methods, enabling comprehensive modeling from mode analysis and optical field manipulation to macroscopic optical properties, thus providing a systematic research framework for investigating light-micro/nano-structure coupling. Based on the design and fabrication of binary arrays on the ZnS surface, enhanced transmittance is achieved in the long-wave infrared region, with interface transmittance improved by 9.3 percentage points in 8?12 mu m, reaching over 97%, and maintaining above 96% across entire 8?14 mu m (Fig. 6). Both simulation and experimental results confirm that binary arrays represent an optimal approach for achieving infrared ultra-broadband AR, highlighting their advantages in design and fabrication, and providing significant guidance for selecting realization pathways and practical applications of broadband AR technologies in the infrared regime. Conclusions This study investigates fundamental requirements for achieving ultra-broadband AR using subwavelength micro-nano structures. The physical mechanism of broadband AR and wavelength-insensitive optical impedance matching processes of moth-eye structures and binary arrays are systematically compared, revealing the origin of their differing height dependences. Through the design of AR micro-nano structures on ZnS and Ge surfaces, the unique advantages of binary arrays as shallow, broadband AR structures are demonstrated. Furthermore, the wavelength band and height prerequisites for realizing broadband AR with binary arrays are clarified. Using a standard semiconductor process, shallow binary arrays with a height of 1.4 mu m (only 67% of the height required for moth-eye structures to achieve equivalent transmittance) are fabricated on ZnS surfaces. The fabricated structures exhibit enhanced transmittance in the long-wave infrared region, with the average interface transmittance in 8?12 mu m increased by 9.3 percentage points to 97%, and the transmittance across the entire 8?14 mu m improved by 8.4 percentage points to 96.2%. These results demonstrate the ultra-broadband AR capability of binary arrays and their excellent compatibility with semiconductor processes, making it a promising candidate for diverse infrared applications.

Semiconductor quantum dots (QDs), a class of quantum-confined nanocrystals, serve as building blocks for the composition of nanomaterials with tunable properties, and are widely used in quantum computing, optoelectronics, and biosensing. Although large-scale synthesis and assembly of colloidal QDs are well-established, precise control of the energy states of single QDs remains challenging, which is important in some forefront applications such as quantum computing that demands robust coherent coupling between QDs. Here, we propose a stress engineering method using a nanoprobe tip to achieve fine-tuned modulation of energy states of single QDs. Specifically, by applying localized uniaxial pressure at the gigapascal level onto a CdSe/ZnS QD, a partial phase transition from wurtzite to zinc-blende structure occurs, leading to an unprecedented irreversible red shift of its bandgap in a wide range exceeding 10 nm. Furthermore, by modulating the applied pressure through controlled amplitude and cycle parameters, we have realized bidirectional spectral tuning or linearly-correlated stepwise tuning of single QD emission peak. Compared with conventional methods that are limited to unidirectional reversible blue shift in bulk QD ensembles, our method offers a versatile and precise strategy for tailoring the emission energy levels of single QDs, effectively meeting the critical requirements for QD-based high-performance photonic devices.

The topological properties of optical spin skyrmions provide an additional degree of freedom for data encoding in photonic networks. Although optical spin skyrmions can be realized at subwavelength scales by surface plasmonics, they fail to radiate into free space as information carriers due to spatial confinement to metal-dielectric interfaces. To date, free-space radiative spin skyrmions have relied on cascaded, bulky optical elements. Here, we report a direct approach to generating free-space optical spin skyrmions using a single surface plasmonic device named a plasmonic geometric phase aperture. Distinct from surface-bound modes, the skyrmion textures of the radiated fields are engineered by spin-orbit interaction in metallic nanoslits via Pancharatnam-Berry geometric phases. It transforms a portion of the circularly polarized waves into a vortex beam that, nested with the residual light, forms spin skyrmion fields, which can be experimentally visualized through spin-selective, phase-resolved scanning near-field optical microscopy. Importantly, the spin skyrmions are generated in the intermediate field region several micrometers above the device surface, bridging the crucial spatial gap between the optical near-field and far-field demanded for on-chip interconnection. The findings provide an ideal solution for high-capacity and robust chip-to-chip optical communications using optical skyrmions.

We demonstrate a snapshot spectral imager based on continuous bound state narrow-band high-transmittance metalens array, capturing 16 image channels simultaneously across the 467–663 nm spectral range using a parallel optical processing approach.

The pursuit of high speed,large capacity,and low power con-sumption of electronic and photonic systems drives the long-term tendency of device miniaturization.

Snapshot spectral imaging is an emerging technology for fast data acquisition in dynamic environments, capturing high‐volume spatial‐spectral information in a single snapshot. However, it suffers from bulky cascading optics and cannot be directly used in space‐restricted scenarios such as endoscope‐assisted brain microsurgery and real‐time cellular tissue imaging. In this work, an ultracompact strategy of parallelized metasurface computed tomography empowered by generative deep learning is proposed, which can effectively reduce the optics volume in snapshot spectral imaging from cm 3 scale to sub‐mm 3 scale while retaining high resolution and speed of imaging so that the above‐mentioned pain point problem is well addressed. The system comprises seven multifunctional sub‐metasurfaces simultaneously acquiring multi‐angle spectral projection and integration information of the target, uses the system‐calibrated point spread functions as wavelength and spatial position distributions, and incorporates a generative adversarial deep neural network for fast reconstruction of spatial‐spectral multiplexed images. Experimental results show that single snapshot imaging can be achieved in 38 ms with a spectral resolution of 10 nm in the spectral range of 450–650 nm. This technique paves the way for snapshot spectral imaging integration into various highly miniaturized microscopy and endoscopic imaging systems in applications such as advanced medical diagnosis.

Blackbodies, ideal light-absorbing objects per Planck's law, do not occur in nature on Earth. Nevertheless, they are of utmost significance in applications across astronomy, optoelectronics, and thermal radiation engineering. While artificial counterparts such as cavity blackbodies and plane blackbodies can approximate ideal blackbodies to some extent, they are beset with problems, including large volume, low emissivity, narrow bandwidth, poor uniformity, and feeble adhesion. Here, a method relying on ultrafast laser direct irradiation is reported, which enables fast writing of uniform plane blackbodies with high-emissivity over 0.98 in an ultra-broadband spectrum of 3-14 µm on a doped silicon surface. A phenomenon of energy negative feedback regulation in laser-material is discovered, which allows for the simultaneous implementation of hierarchical surface structuring and nanodefect-induced energy-level engineering. The resulting micro-nano hierarchical cone-array structure effectively curbs light back-scattering and intensifies nanodefect-induced absorption. Since the laser-treated surface does not entail material adhesion or injection, it exhibits superior stability in contrast to traditional black coatings. This is corroborated by high-temperature tests exceeding 900 °C and repeated mechanical exfoliation tests, underscoring its resilience in harsh environmental conditions.

We introduce a pixelated metasurface filter array based on narrowband high-transmittance continuous bound states, integrated onto a detector to achieve real-time spectral imaging without computational reconstruction.

Atomic force microscope (AFM) generally works on the basis of manipulating absolute magnitude of van der Waals (vdW) force between the tip and specimen. The force is, however, less sensitive to alternation of atom species than to tip-sample separations, resulting in the difficulty of compositional identification, even under multi-modal strategies and other AFM variations. Here, we report a phenomenon of light enhancement of van der Waals force (LvF), and the enhancement factor is found specific to materials. The force difference prior and after illumination, instead of the tip-specimen force itself, is employed for discriminating heterogeneous phases. The corresponding LvF microscopy (LvFM) demonstrates not only a ultra-high compositional resolution represented by 20 dB enhancement factor and 150 times of the detection limit, but also a sub-10 nm lateral spatial resolution much smaller than the tip size of 20 nm. The simplicity of the opto-thermal mechanism, minuteness of excitation light power and wide availability of boosting lasers at various wavelengths imply broad applications of LvFM on nano-materials characterization, particularly on two-dimensional semiconductors that are promising as new generation of chip materials.

The stability and emissivity of the online calibration blackbody used in high-precision infrared remote sensing detectors in extreme environments are the primary limiting factors for their measurement accuracy. Due to the limitations of microstructure size effects, traditional calibration extended area blackbody cannot achieve an optimal balance between emissivity and stability, thus hindering further improvement in infrared remote sensing accuracy. This work proposes a new method that utilize suppressing near-field backscattering to control far-field reflectance. Specifically, through simultaneously reducing backscattering intensity and the backscattering solid angle, the reflectance is significantly reduced to an extremely low limit, which is validated through numerical simulations. Additionally, by combining the femtosecond laser self-convergent processing technique, the spontaneous energy negative feedback mechanism during femtosecond laser processing is utilized to achieve the fabrication of a high emissivity, thermally stable, mechanically stable, and highly uniform extended area blackbody. The blackbody fabricated using this technique can be applied for online calibration in various extreme environments, significantly improving measurement accuracy and service life.

Snapshot spectral imaging technology enables the capture of complete spectral information of objects in an extremely short period of time, offering wide-ranging applications in fields requiring dynamic observations such as environmental monitoring, medical diagnostics, and industrial inspection. In the past decades, snapshot spectral imaging has made remarkable breakthroughs with the emergence of new computational theories and optical components. From the early days of using various spatial-spectral data mapping methods, they have evolved to later attempts to encode various dimensions of light, such as amplitude, phase, and wavelength, and then computationally reconstruct them. This review focuses on a systematic presentation of the system architecture and mathematical modeling of these snapshot spectral imaging techniques. In addition, the introduction of metasurfaces expands the modulation of spatial-spectral data and brings advantages such as system size reduction, which has become a research hotspot in recent years and is regarded as the key to the next-generation snapshot spectral imaging techniques. This paper provides a systematic overview of the applications of metasurfaces in snapshot spectral imaging and provides an outlook on future directions and research priorities.

Two-dimensional (2D) semiconductors, such as transition metal dichalcogenides, have emerged as important candidate materials for next-generation chip-scale optoelectronic devices with the development of large-scale production techniques, such as chemical vapor deposition (CVD). However, 2D materials need to be transferred to other target substrates after growth, during which various micro- and nanoscale defects, such as nanobubbles, are inevitably generated. These nanodefects not only influence the uniformity of 2D semiconductors but also may significantly alter the local optoelectronic properties of the composed devices. Hence, super-resolution discrimination and characterization of nanodefects are highly demanded. Here, we report a near-field nanophotoluminescence (nano-PL) microscope that can quickly screen nanobubbles and investigate their impact on local excitonic properties of 2D semiconductors by directly visualize the PL emission distribution with a very high spatial resolution of ∼10 nm, far below the optical diffraction limit, and a high speed of 10 ms/point under ambient conditions. By using nano-PL microscopy to map the exciton and trion emission intensity distributions in transferred CVD-grown monolayer tungsten disulfide (1L-WS2) flakes, it is found that the PL intensity decreases by 13.4% as the height of the nanobubble increases by every nanometer, which is mainly caused by the suppression of trion emission due to the strong doping effect from the substrate. In addition to the nanobubbles, other types of nanodefects, such as cracks, stacks, and grain boundaries, can also be characterized. The nano-PL method is proven to be a powerful tool for the nondestructive quality inspection of nanodefects as well as the super-resolution exploration of local optoelectronic properties of 2D materials.

Excitons are quasi-particles composed of electron-hole pairs through Coulomb interaction. Due to the atomic-thin thickness, they are tightly bound in monolayer transition metal dichalcogenides (TMDs) and dominate their optical properties. The capability to manipulate the excitonic behavior can significantly influence the photon emission or carrier transport performance of TMD-based devices. However, on-demand and region-selective manipulation of the excitonic states in a reversible manner remains challenging so far. Herein, harnessing the coordinated effect of femtosecond-laser-driven atomic defect generation, interfacial electron transfer, and surface molecular desorption/adsorption, we develop an all-optical approach to manipulate the charge states of excitons in monolayer molybdenum disulfide (MoS2). Through steering the laser beam, we demonstrate reconfigurable optical encoding of the excitonic charge states (between neutral and negative states) on a single MoS2 flake. Our technique can be extended to other TMDs materials, which will guide the design of all-optical and reconfigurable TMD-based optoelectronic and nanophotonic devices.

Achieving higher brightness of a single-photon emitter (SPE) is central for advanced applications from quantum information processing to quantum sensing. However, most approaches of integrating quantum emitters and photonic resonators require accurately localizing the emitter into a photonic structure, which is a challenge. Here, we report using dielectric microspheres for laser focusing to create SPEs in hexagonal boron nitride and in situ enhance the emission via photonic coupling between the SPE and the dielectric microspheres. The photoluminescence intensity is increased by 2.4-fold, achieving a high brightness SPE with a saturation intensity of up to 19.6 Mcounts s−1. This approach provides a feasible way to generate a high-performance SPE while simultaneously enabling precise coupling of the quantum light source and optical resonators.

Photonic nano/microstructures (e [...].