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The carbon–carbon (C–C) bond formation is essential for the electroconversion of CO2 into high-energy-density C2+ products, and the precise coupling pathways remain controversial. Although recent computational investigations have proposed that the OC–COH coupling pathway is more favorable in specific reaction conditions than the well-known CO dimerization pathway, the experimental evidence is still lacking, partly due to the separated catalyst design and mechanistic/spectroscopic exploration. Here, we employ density functional theory calculations to show that on low-coordinated copper sites, the *CO bindings are strengthened, and the adsorbed *CO coupling with their hydrogenation species, *COH, receives precedence over CO dimerization. Experimentally, we construct a fragmented Cu catalyst with abundant low-coordinated sites, exhibiting a 77.8% Faradaic efficiency for C2+ products at 300 mA cm–2. With a suite of in situ spectroscopic studies, we capture an *OCCOH intermediate on the fragmented Cu surfaces, providing direct evidence to support the OC–COH coupling pathway. The mechanistic insights of this research elucidate how to design materials in favor of OC–COH coupling toward efficient C2+ production from CO2 reduction.

Inspired by transformation optics, we propose a new concept for plasmonic photocatalysis by creating a novel hybrid nanostructure with a plasmonic singularity. Our geometry enables broad and strong spectral light harvesting at the active site of a nearby semiconductor where the chemical reaction occurs. A proof-of-concept nanostructure comprising Cu2ZnSnS4 (CZTS) and Au-Au dimer (t-CZTS@Au-Au) is fabricated via a colloidal strategy combining templating and seeded growth. On the basis of numerical and experimental results of different related hybrid nanostructures, we show that both the sharpness of the singular feature and the relative position to the reactive site play a pivotal role in optimizing photocatalytic activity. Compared with bare CZTS, the hybrid nanostructure (t-CZTS@Au-Au) exhibits an enhancement of the photocatalytic hydrogen evolution rate by up to ∼9 times. The insights gained from this work might be beneficial for designing efficient composite plasmonic photocatalysts for diverse photocatalytic reactions.

Optical hotspots underpin a wide variety of photonic devices ranging from sensing, nonlinear generation to photocatalysis, taking advantage of the strong light-matter interaction at the vicinity of photonic nanostructures. While plasmonic nanostructures have been widely used for strongly localized electromagnetic energy on surfaces, they suffer from high loss and consequently a low quality factor. Resonance-based dielectric structures provide an alternative solution with a larger quality factor, but there is a mismatch between the maximum values of the light confinement (quality factor) and the leakage (intensity in the near-field). Here, we propose to apply the concept of topological photonics to the formation of hotspots, producing them in both topological edge states and topological corner states. The topology secures strong light localization at the surface of the nanostructures where the underlying topological invariant shows a jump, generating a field hotspot with simultaneous increment of quality factor and light intensity. Meanwhile, it leverages a good robustness to fabrication imperfection including fluctuation in shape and misalignment. After a systematic investigation and comparison of the robustness between 1D and 2D topological structures, we conclude that the hotspots from 1D topological edge states promise a fertile playground for emerging applications that require both enhanced light intensity and high spectral resolution.

Skyrmions endowed with topological protection have been extensively investigated in various platforms including magnetics, ferroelectrics, and liquid crystals, stimulating applications such as memories, logic devices, and neuromorphic computing. While the optical counterpart has been proposed and realized recently, the study of optical skyrmions is still in its infancy. Among the unexplored questions, the investigation of the topology induced robustness against disorder is of substantial importance on both fundamental and practical sides but remains elusive. In this Letter, we manage to generate optical skyrmions numerically in real space with different topological features at will, providing a unique platform to investigate the robustness of various optical skyrmions. A disorder-induced topological state transition is observed for the first time in a family of optical skyrmions composed of six classes with different skyrmion numbers. Intriguingly, the optical skyrmions produced from a vectorial hologram are exceptionally robust against scattering from a random medium, shedding light on topological photonic devices for the generation and manipulation of robust states for applications including imaging and communication.

For a repertoire of nanophotonic systems, including photonic crystals, metasurfaces, and plasmonic structures, unit cell with a single element is conventionally used for the simplicity of design. The extension of the unit cell with multiple meta-atoms drastically enlarges the parameter space and consequently provides potential configurations with improved device performance. Simultaneously, the multiplication does not induce additional complexity for lithography-based fabrications. However, the substantially increased number of parameters makes the design methodology based on physical intuition and parameter sweep impractical. Here, we show that expanding the number of meta-atoms in the unit cell significantly improves the performance of nanophotonic systems by the virtue of a genetic algorithm-based optimizer. Our approach includes physical intuition endowed in the geometry of meta-atoms, providing additional physical understanding of the optimization process. We demonstrate two photonic applications, including prominent enhancement of a broadband absorption and enlargement of the color coverage of plasmonic nanostructures. Not limited to the two proof-of-concept demonstrations, this methodology can be applied to all meta-atom-based nanophotonic systems, including plasmonic near-field enhancement and nonlinear frequency conversion, as well as a simultaneous control of phase and polarization for metasurfaces.

With the advancement in understanding of the physics inside chaotic systems, chaos has been harnessed from a nuisance to a beneficial factor in optical devices. Light–matter interaction in chaotic systems has been utilised for improving broadband energy harvesting and momentum transformations, achieving light localization beyond diffraction limit and even stabilizing the dynamics of high power laser. While extensive study about wave chaos has been made in deformed microcavities, investigation of how chaos dynamics evolves in curved space manifold remains elusive. Here, we study the non-Euclidean billiard of a torus-like manifold, which is a closed 2D cavity system with effective periodic boundaries. The ray chaotic behaviours on the deformed toroidal surface are explored using the geodesic equation. By tuning the deformation parameter of the torus, we observe the transition of the billiard from the ordered phase state to mixed phase states and then complete ray chaos. The photon sphere of the torus is identified as the transition position from ordered states to chaotic states. Compared with other chaotic behaviours resulted from the random scattering inside deformed cavities, we demonstrate chaotic dynamics purely on a curved surface, which may shed light on the better understanding of chaos in optics.

Constructing plasmonic-semiconductor nanoarchitecture provides a photocatalytic platform for enhancing solar energy conversion. The excitation and extraction of energetic carriers are critical for improving energy efficiency, which can be affected by the geometric features of plasmonic structures. An extensive study on morphology dependent hot electron utilization is desirable but challenging. In this paper, we applied photocurrent response from the microscale reaction region on Au-TiO2 photoanode to evaluate the influence of plasmonic morphology in water splitting. We compared the photocurrent of two structures, gold nanospheres and nanorods, under visible illumination. We experimentally proved that the nanorods demonstrate better energy performance. The possible origins of this enhancement are ascribed to the sharp curvature at tips, where strong hot spots boost the generation and injection efficiency of hot electrons. These results may pave a way for a rational geometry design for plasmonic enhanced photocatalysis.

Electrochemical CO

Intuitively, the variation of boundary conditions in differential equations produces different solutions. For Maxwell’s equations, changes of the permittivity (or refractive index) induce different optical dynamics for both bulk materials and nanostructures.

Objective: The immunoscore, which is used to quantify immune infiltrates, has greater relative prognostic value than tumor, node, and metastasis (TNM) stage and might serve as a new system for classification of colorectal cancer. However, a comparable immunoscore for predicting lung adenocarcinoma (LUAD) prognosis is currently lacking. Methods: We analyzed the expression of 18 immune features by immunohistochemistry in 171 specimens. The relationship of immune marker expression and clinicopathologic factors to the overall survival (OS) was analyzed with the Kaplan-Meier method. A nomogram was developed by using the optimal features selected by least absolute shrinkage and selection operator (LASSO) regression in the training cohort (n = 111) and evaluated in the validation cohort (n = 60). Results: The indicators integrated in the nomogram were TNM stage, neuron-specific enolase, carcino-embryonic antigen, CD8center of tumor (CT), CD8invasive margin (IM), FoxP3CT, and CD45ROCT. The calibration curve showed prominent agreement between the observed 2- and 5-year OS and that predicted by the nomogram. To simplify the nomogram, we developed a new immune-serum scoring system (I-SSS) based on the points awarded for each factor in the nomogram. Our I-SSS was able to stratify same-stage patients into different risk subgroups. The combination of I-SSS and TNM stage had better prognostic value than the TNM stage alone. Conclusions: Our new I-SSS can accurately and individually predict LUAD prognosis and may be used to supplement prognostication based on the TNM stage.

To examine the clinicopathologic and immunohistochemical features of a group of newly defined low-grade oncocytic renal tumors (LOT) that have the "CD117 negative/cytokeratin (CK)7 positive" immunoprofile. We have queried our hospital database and found 4456 consecutive renal tumors between 2016 and 2019. Among these renal tumors, eight (8) cases meet the morphologic and immunohistochemical characterization for low-grade oncocytic renal tumor (LOT). The eight (8) patients' mean age is 56.6 years (range 39-70 years old), and the male to female ratio is 1:1. Macroscopically, these LOTs generally present with tan-brown and solid cut surfaces and demonstrate similar solid, compact nested growth pattern microscopically. Tumor cells exhibit oncocytic cytoplasm and uniformly rounded to oval nuclei. There are areas of edematous stroma containing dispersed single or small clustered tumor cells. All tumors are negative for CD117 and positive for CK7. Uniform reactivity is also found for BerEP4, cyclin D1, and SDHB. Besides, CD10, vimentin, and AMACR are either negative or only focally positive. All of the tumors are negative for CA9 and TFE. The Ki-67 index is less than 5% in the seven (7) internal cases. Seven (7) of the eight (8) patients who are available for follow-up are alive and without disease recurrence (mean follow-up period of 21.6 months, ranging from 6 to 43 months). We described a group of low-grade oncocytic renal tumors identified retrospectively in a large tertiary cancer center, which was probably the first report originated from China or even Asia in the English literature so far. These tumors demonstrated eosinophilic cytoplasm and low-grade appearing nuclei with a "CD117 negative/CK7 positive" immunoprofile. The incidence rate was about 3.7% of the oncocytic renal tumors and 0.18% of all the renal tumors that were received in our lab during the four-year period. It is necessary to separate this group of tumors by its characteristic morphologic and immunophenotypic features.

Our previous work demonstrated that Epithelial Splicing Regulatory Protein 1 (ESRP1) could inhibit the progression of lung adenocarcinoma (ADC). When ESRP1 was upregulated, the interferon (IFN) pathway was activated and Interferon-stimulated gene 15 (ISG15) expression increased exponentially in our microarray result. In this study, we aim to explore the function of ISG15 and its interactions with ESRP1 and to provide new insights for ADC treatment. ISG15 expression in lung ADC tissues was determined by immunohistochemistry (IHC) staining. The effect of ISG15 on lung ADC progression was examined by in vitro and in vivo assays. The mechanism of action on ESRP1 regulating ISG15 was investigated using Western blotting, RT-qPCR, immunofluorescence staining, chromatin immunoprecipitation, and a dual luciferase reporter system. The ISGylation between ISG15 and ESRP1 was detected by co-immunoprecipitation. Patients with high ISG15 expression were associated with higher survival rates, especially those with ISG15 expression in the nucleus. In vitro and in vivo experiments showed that upregulation of ISG15 inhibited EMT in lung ADC. ESRP1 upregulated the expression of ISG15 through CREB with enriched ISG15 in the nucleus. Importantly, ISG15 promoted ISGylation of ESRP1 and slowed the degradation of ESRP1, which demonstrated that ESRP1 and ISG15 formed a positive feedback loop and jointly suppressed EMT of lung ADC. In conclusion, ISG15 serves as an independent prognostic marker for long-term survival in lung ADC patients. We have revealed the protective effect of ISG15 against lung ADC progression and the combinatorial benefit of ISG15 and ESRP1 on inhibiting EMT. These findings suggest that reconstituting ISG15 and ESRP1 may have the potential for treating lung ADC.

Plasmonic nanostructures possessing broadband intense field enhancement over a large area are highly desirable for nanophotonic and plasmonic device applications. In this study, 3D Ag hybrid nanoaggregates (3D-Ag-HNAs) are achieved via a highly efficient oblique angle gas-phase cluster beam deposition method. Not only can such structures produce a high density of plasmonic hot-spots to improve Raman sensitivity, but more importantly they generate kissing point-geometric singularities with a broadband optical response. We succeed in obtaining an experimental SERS enhancement factor beyond 4 × 107 in the visible range, providing an optimal sensing platform for different analytes. Combined with good uniformity, reproducibility and ease of fabrication, our 3D-Ag-HNA offers a candidate for new generations of SERS systems.

Disordered biostructures are ubiquitous in nature, usually generating white or black colours due to their broadband optical response and robustness to perturbations. Through judicious design, disordered nanostructures have been realised in artificial systems, with unique properties for light localisation, photon transportation and energy harvesting. On the other hand, the tunability of disordered systems with a broadband response has been scarcely explored. Here, we achieve the controlled manipulation of disordered plasmonic systems, realising the transition from broadband absorption to tunable reflection through deterministic control of the coupling to an external cavity. Starting from a generalised model, we realise disordered systems composed of plasmonic nanoclusters that either operate as a broadband absorber or with a reconfigurable reflection band throughout the visible. Not limited to its significance for the further understanding of the physics of disorder, our disordered plasmonic system provides a novel platform for various practical application such as structural colour patterning., The tunability of disordered systems with a broadband response has not been explored. Here, the authors achieve the controlled manipulation of disordered plasmonic systems, realising a transition from broadband absorption to tunable reflection through control of the coupling to an external cavity.

Organic-inorganic perovskites have arrived at the forefront of solar technology due to their impressive carrier lifetimes and superior optoelectronic properties. By having the cm-sized perovskite single crystal and employing device patterning techniques, and the transfer length method (TLM), we are able to get the insight into the metal contact and carrier transport behaviors, which is necessary for maximizing device performance and efficiency. In addition to the metal work function, we found that the image force and interface charge pinning effects also affect the metal contact, and the studied single crystal CH3NH3PbBr3 features Schottky barriers of 0.17 eV, 0.38 eV, and 0.47 eV for Au, Pt, and Ti electrodes, respectively. Furthermore, the surface charges lead to the thermally activated transport from 207 K to 300 K near the perovskite surface. In contrast, from 120 K to 207 K, the material exhibited three-dimensional (3D) variable range hopping (VRH) carrier transport behavior. Understanding these fundamental contact and transport properties of perovskite will enable future electronic and optoelectronic applications.

A novel ultra-supercritical circulating fluidized bed (CFB) boiler technology based on recycling the high-temperature internal solids in the dense-phase zone to heat final superheater and reheater was investigated in this paper. The merit of this technology was that it can guarantee the superheated and reheated steam outlet temperatures especially under the low load condition. The flow characteristics of internal solids circulation was investigated on a cold test rig using the circulating solids from the Baima's 600 MW supercritical CFB boiler and the valid internal solids circulation rate was measured by optical fiber probes. The effects of fluidizing air velocity, partition height and static main bed height on the valid internal solids circulation rate were studied. Moreover, the valid internal solids circulation rate of thermal state was measured on the Baima's 600 MW supercritical CFB boiler. By the cold and thermal tests, an empirical formula which could predict the valid internal solids circulation rate was summarized and refined. In addition, the heat exchange ability of internal solids circulation was analyzed and the needed internal solids circulation rate of actual boiler was calculated. Besides, practicable schemes of this technology were proposed in the end of the paper. Based on the above analysis, it was proved that the novel technology using the internal solids circulation was feasible to guarantee the temperatures of final superheated and reheated steam in an ultra-supercriticalCFB boiler.

Gas-solid flow characteristics at the riser wall were studied in a 60-meter-high transparent circulating fluidized bed (CFB) riser. The flowing processes of clusters were recorded by a high-speed camera. Through analyzing the pictures obtained in the 60 m riser, the coverage fraction of clusters at the riser wall fc, the descent velocities of clusters at the riser wall Uc, the cluster-wall contact length Lc and the cluster-wall contact time τc were measured. Based on the experimental data, empirical formulas for estimating fc, Uc, Lc in the 60 m riser (10 m above the distributor) were proposed. The results showed that both Uc and Lc obtained in the 60 m riser (10 m above the distributor) were larger than those obtained in risers lower than 15 m.τc varied between 0.07 s and 0.20 s under the experimental conditions.

Despite the development of various treatments, metastasis remains a significant problem with lung adenocarcinoma (ADC). The role and mechanism of epithelial splicing regulatory protein 1 (ESRP1), an epithelial-specific RNA binding protein, on promoting the invasion and metastasis of lung ADC remain to be fully elucidated. Immunohistochemical analysis in 125 human lung ADC tissue samples demonstrated that ESRP1 overexpression was inversely related to the presence of metastases, tumor size, and clinical stage of lung ADC. Impaired ESRP1 expression was also found to stimulate the invasion capacity of lung ADC cells both in vitro and in vivo. Functionally, overexpression of the ZEB1 gene decreased ESRP1 expression, and knockdown of the ZEB1 gene caused increased ESRP1 expression. On the basis of a gene array analysis, the expression of ESRP1 was associated with the regulation of the extracellular matrix. The expression of CD44 and fibroblast growth factor receptor, representatives that interact with the extracellular matrix, was studied. The CD44 subtypes promoted lung ADC cell invasion by regulating matrix metalloproteinase 2 expression. In conclusion, ESRP1 inhibits the invasion and metastasis of lung ADC and plays a role in regulating proteins involved in epithelial-to-mesenchymal transition.

ObjectivesThe purpose of this study was to distinguish synchronous primary endometrial and ovarian carcinomas from single primary tumor with metastasis by clinical pathologic criteria and whole exome sequencing (WES).Material and MethodsFifty-two patients with synchronous endometrial and ovarian carcinomas (SEOCs) between 2010 and 2017 were reviewed and subjected to WES.ResultsOn the basis of the Scully criteria, 11 cases were supposed as synchronous primary endometrial and ovarian carcinomas, 38 cases as single primary tumor with metastasis, and the remaining 3 cases (S50–S52) cannot be defined. Through a quantization scoring analysis, 9 cases that were scored 0–1 point were defined as synchronous primary endometrial and ovarian carcinomas, and 42 cases that were scored 3–8 points were defined as single primary tumor with metastasis. Two of the undefined cases were classified into metastatic disease, and another one that scored 2 points (S52) was subjected to WES. S52 was deemed synchronous primary endometrial and ovarian carcinomas, with few shared somatic mutations and overlapping copy number varieties. The finding of a serous component examined from the uterine endometrium samples further illustrated that the case was synchronous primary endometrial and ovarian carcinomas.ConclusionBy scoring criterion, SEOCs were divided into 2 groups: synchronous primary endometrial and ovarian carcinoma group and single primary tumor with metastasis group. The analysis of clonality indicated that the case that scored 2 (S52) can be considered as synchronous primary endometrial and ovarian carcinomas. Scoring criteria of clinical pathology, along with the study of the WES, may further identify the classification of SEOCs.

Extragonadal primary yolk sac tumor of the intestinal tract origin is exceedingly rare. Through a multiple disciplinary team, the diagnosis and treatment of primary intestinal yolk sac tumor were further defined. We report 2 such cases with detailed histologic and immunohistochemical analysis. The two patients were a 7-year-old girl and a 29-year-old woman. Both of them preoperatively had an elevated serum alpha fetoprotein (AFP) level (≥ 1,210 ng/mL). The tumors are located in the intestine and imaging examination indicated the rectum as the primary site. Grossly the mass was grey-white and crisp texture. Microscopic examination featured reticular, microcystic, macrocystic, papillary, solid, and some glandular patterns. Immunohistochemically, tumor cells of both cases were positive for SALL4, AFP, pan-cytokeratin (AE1/AE3), and glypican-3. Simultaneously, a stain for EMA, OCT4, CD30, HCG, vimentin and CK20 were negative in all 2 neoplasms. The features of morphology, immunohistochemistry, laboratory examinations and imaging studies consist of the diagnosis of primary yolk sac tumor of the intestine.

Nonsense-mediated mRNA decay (NMD) is a highly conserved pathway that selectively degrades aberrant RNA transcripts. In this study, we proved that NMD regulates the epithelial-mesenchymal transition (EMT) of lung adenocarcinoma (ADC). Moreover, we found that NMD core factor UP-frameshift 1 tends to be expressed at lower levels in human ADC tissues than in normal lung tissues, thereby raising the possibility that NMD may be downregulated to permit ADC oncogenesis. Our experiments in human ADC cell lines showed that downregulating NMD can promote EMT. Moreover, EMT can be inhibited by upregulating NMD. We tested the role of TGF-ß signaling and found that NMD influences EMT by targeting the TGF-ß signaling pathway. Our findings reveal that NMD is a potential tumor regulatory mechanism and may be a potential therapeutic target for ADC.

Weyl points are discrete locations in the three-dimensional momentum space where two bands cross linearly with each other. They serve as the monopoles of Berry curvature in the momentum space, and their existence requires breaking of either time-reversal or inversion symmetry1–16. Although various non-centrosymmetric Weyl systems have been reported15, demonstration of Weyl degeneracies due to breaking of the time-reversal symmetry remains scarce and is limited to electronic systems17,18. Here, we report the experimental observation of photonic Weyl degeneracies in a magnetized semiconductor—InSb, which behaves as a magnetized plasma19 for electromagnetic waves at the terahertz band. By varying the magnetic field strength, Weyl points and the corresponding photonic Fermi arcs have been demonstrated. Our observation establishes magnetized semiconductors as a reconfigurable20 terahertz Weyl system, which may prompt research on novel magnetic topological phenomena such as chiral Majorana-type edge states and zero modes in classic systems21,22. Photonic Weyl points—topologically chiral singularity points in three-dimensional momentum space—have been realized in a homogeneous non-reciprocal material without a crystal lattice structure.

The mathematical concept of fractals is widely applied to photonics as planar structures ranging from terahertz resonators, optical antennas, to photodetectors. Here, instead of a direct mathematical abstract, we design a plasmonic leaf with fractal geometry from the outline of a leaf from Wargrave Pink. The enhanced light-matter interactions are observed numerically from the improvement in both absorption and near-field intensification. To demonstrate the effect experimentally, a three-dimensional fractal structure is realised through direct laser writing, which significantly improves the photothermal conversion. By virtue of the self-similarity in geometry, the artificial leaf improves the absorption of a 10-nm-thick gold film with 14 × temperature increment compared to flat Au film. Not limited to the proof-of-concept photothermal experiment demonstrated here, the fractal structure with improved light-matter interactions can be utilised in a variety of applications ranging from non-linear harmonic generation, plasmonic-enhanced fluorescence, to hot electron generation for photocatalysis.

When the feature size of photonic structures becomes comparable or even smaller than the wavelength of light, the fabrication imperfections inevitably introduce disorder that may eliminate many functionalities of subwavelength photonic devices. Here we suggest a novel concept to achieve a robust bandgap which can endure disorder beyond 30 as a result of the transition from photonic crystals to Mie-resonant metamaterials. By utilizing Mie-resonant metamaterials with high refractive index, we demonstrate photonic waveguides and cavities with strong robustness to position disorder, thus providing a novel approach to the bandgap-based nanophotonic devices with new properties and functionalities., Comment: 6 pages, 5 figures

Topological circuits, an exciting field just emerged over the last two years, have become a very accessible platform for realizing and exploring topological physics, with many of their physical phenomena and potential applications as yet to be discovered. In this work, we design and experimentally demonstrate a topologically nontrivial band structure and the associated topologically protected edge states in an RF circuit, which is composed of a collection of grounded capacitors connected by alternating inductors in the x and y directions, in analogy to the Su–Schrieffer–Heeger model. We take full control of the topological invariant (i.e., Zak phase) as well as the gap width of the band structure by simply tuning the circuit parameters. Excellent agreement is found between the experimental and simulation results, both showing obvious nontrivial edge state that is tightly bound to the circuit boundaries with extreme robustness against various types of defects. The demonstration of topological properties in circuits provides a convenient and flexible platform for studying topological materials and the possibility for developing flexible circuits with highly robust circuit performance.

The interaction of light with nanostructured materials provides exciting new opportunities for investigating classical wave analogies of quantum phenomena. A topic of particular interest forms the interplay between wave physics and chaos in systems where a small perturbation can drive the behavior from the classical to chaotic regime. Here, we report an all-optical laser-driven transition from order to chaos in integrated chips on a silicon photonics platform. A square photonic crystal microcavity at telecom wavelengths is tuned from an ordered into a chaotic regime through a perturbation induced by ultrafast laser pulses in the ultraviolet range. The chaotic dynamics of weak probe pulses in the near infrared is characterized for different pump-probe delay times and at various positions in the cavity, with high spatial accuracy. Our experimental analysis, confirmed by numerical modelling based on random matrices, demonstrates that nonlinear optics can be used to control reversibly the chaotic behavior of light in optical resonators

Engineering hotspots is of crucial importance in many applications including energy harvesting, nano-lasers, subwavelength imaging, and biomedical sensing. Surface-enhanced Raman scattering spectroscopy is a key technique to identify analytes that would otherwise be difficult to diagnose. In standard systems, hotspots are realised with nanostructures made by acute tips or narrow gaps. Owing to the low probability for molecules to reach such tiny active regions, high sensitivity is always accompanied by a large preparation time for analyte accumulation which hinders the time response. Inspired by transformation optics, we introduce an approach based on warped spaces to manipulate hotspots, resulting in broadband enhancements in both the magnitude and volume. Experiments for single molecule detection with a fast soaking time are realised in conjunction with broadband response and uniformity. Such engineering could provide a new design platform for a rich manifold of devices, which can benefit from broadband and huge field enhancements., In standard SERS the probability for the molecules to reach tiny hotpot regions is low. Here, the authors introduce an approach based on warped spaces that offers a strategy to manipulate hotspots of metallic nanostructures, resulting in large broadband enhancements in both the magnitude and the volume size.

Wave dynamics on curved surfaces has attracted growing attention due to its close resemblance to the warped space time governed by general relativity. It also opens up opportunities for designing functional optical devices such as geodesic lenses. In this work we study the wave dynamics on the surface of a torus, a shape of considerable interest due to its nontrivial topology. Governed by the conservation of angular momentum, light propagates on the torus in two different types of modes: one is able to twist around and sweep through the whole surface of the torus; the other is confined within a certain angular range along the torus latitude direction. The confined mode exhibits an interesting self focusing or imaging behavior, which, similar to a geometric lens, shows no dependence of wavelength and thus suffers no chromatic aberration. By changing the geometric parameters of the torus, both the focusing point and the focusing distance can be controlled. Our work provides a new approach to manipulation of light propagation on a curved surface under the conservation of angular momentum.

Transition metal dichalcogenides with intrinsic spin-valley degrees of freedom hold great potentials for applications in spintronic and valleytronic devices. MoS

Engineering broadband light absorbers is crucial to many applications, including energy-harvesting devices and optical interconnects. The performances of an ideal absorber are that of a black body, a dark material that absorbs radiation at all angles and polarizations. Despite advances in micrometre-thick films, the absorbers available to date are still far from an ideal black body. Here, we describe a disordered nanostructured material that shows an almost ideal black-body absorption of 98-99% between 400 and 1,400 nm that is insensitive to the angle and polarization of the incident light. The material comprises nanoparticles composed of a nanorod with a nanosphere of 30 nm diameter attached. When diluted into liquids, a small concentration of nanoparticles absorbs on average 26% more than carbon nanotubes, the darkest material available to date. By pumping a dye optical amplifier with nanosecond pulses of ∼100 mW power, we harness the structural darkness of the material and create a new type of light source, which generates monochromatic emission (∼5 nm wide) without the need for any resonance. This is achieved through the dynamics of light condensation in which all absorbed electromagnetic energy spontaneously generates single-colour energy pulses.

The topological state transition has been widely studied based on the quantized topological band invariant such as the Chern number for the system without intense randomness that may break the band structures. We numerically demonstrate the disorder-induced state transition in the photonic topological systems for the first time. Instead of applying the ill-defined topological band invariant in a disordered system, we utilize an empirical parameter to unambiguously illustrate the state transition of the topological metamaterials. Before the state transition, we observe a robust surface state with well-confined electromagnetic waves propagating unidirectionally, immune to the disorder from permittivity fluctuation up to 60% of the original value. During the transition, a hybrid state composed of a quasiunidirectional surface mode and intensively localized hot spots is established, a result of the competition between the topological protection and Anderson localization.