Abstract
Topological photonics provides a fundamental framework for robust manipulation of light, including directional transport and localization with built-in immunity to disorder. Combined with an ...optical gain, active topological cavities hold special promise for a design of light-emitting devices. Most studies to date have focused on lasing at topological edges of finite systems or domain walls. Recently discovered higher-order topological phases enable strong high-quality confinement of light at the corners. Here, we demonstrate lasing action of corner states in nanophotonic topological structures. We identify several multipole corner modes with distinct emission profiles via hyperspectral imaging and discern signatures of non-Hermitian radiative coupling of leaky topological states. In addition, depending on the pump position in a large-size cavity, we generate selectively lasing from either edge or corner states within the topological bandgap. Our studies provide the direct observation of multipolar lasing and engineered collective resonances in active topological nanostructures.
The fundamental challenge in designing transparent pressure sensors is the ideal combination of high optical transparency and high pressure sensitivity. Satisfying these competing demands is commonly ...achieved by a compromise between the transparency and usage of a patterned dielectric surface, which increases pressure sensitivity, but decreases transparency. Herein, a design strategy for fabricating high‐transparency and high‐sensitivity capacitive pressure sensors is proposed, which relies on the multiple states of nanoparticle dispersity resulting in enhanced surface roughness and light transmittance. We utilize two nanoparticle dispersion states on a surface: (i) homogeneous dispersion, where each nanoparticle (≈500 nm) with a size comparable to the visible light wavelength has low light scattering; and (ii) heterogeneous dispersion, where aggregated nanoparticles form a micrometer‐sized feature, increasing pressure sensitivity. This approach is experimentally verified using a nanoparticle‐dispersed polymer composite, which has high pressure sensitivity (1.0 kPa–1), and demonstrates excellent transparency (>95%). We demonstrate that the integration of nanoparticle‐dispersed capacitor elements into an array readily yields a real‐time pressure monitoring application and a fully functional touch device capable of acting as a pressure sensor‐based input device, thereby opening up new avenues to establish processing techniques that are effective on the nanoscale yet applicable to macroscopic processing.
A design strategy for fabricating high‐transparency and high‐sensitivity capacitive pressure sensors is proposed, which relies on the multiple states of nanoparticle dispersity resulting in enhanced surface roughness and light transmittance. This approach is experimentally verified using a nanoparticle‐dispersed polymer composite, which, despite its low dielectric constant (≈3.0), has high pressure sensitivity (1.0 kPa−1) and demonstrates excellent transparency (>95%).
Responsive photonic crystals (PCs) have attracted much attention due to their broad applications in the field of chemical and physical sensing through varying optical properties when exposed to ...external stimuli. In particular, assembly of block copolymers (BCPs) has proven to be a robust platform for constructing PCs in the form of films or bulk. Here, the generation of BCPs photonic microspheres is presented with 3D periodical concentric lamellar structures through confined self‐assembly. The structural color of the spherical PCs can be tuned by selective swelling of one block, yielding large change of optical property through varying both layer thickness and refraction index of the domains. The as‐formed spherical PCs demonstrate large reflection wavelength shift (≈400–700 nm) under organic solvent permeation and pH adjustment. Spherical shape and structural symmetry endow the formed spherical PCs with rotation independence and monochrome, which is potentially useful in the fields of displays, sensing, and diagnostics.
Block copolymer photonic microspheres with onion‐like structure are generated via confined assembly. The structural color of the responsive photonic crystals (PCs) can be tuned by selective swelling, yielding large optical tunability by varying layer thickness and refraction index of the domains. The formed spherical PCs demonstrate a large reflection wavelength shift under solvent permeation and pH adjustment, as well as rotation independence. They are potentially useful in displays, sensing, and diagnostics.
Nanolasers are key elements in the implementation of optical integrated circuits owing to their low lasing thresholds, high energy efficiencies, and high modulation speeds. With the development of ...semiconductor wafer growth and nanofabrication techniques, various types of wavelength‐scale and subwavelength‐scale nanolasers have been proposed. For example, photonic crystal lasers and plasmonic lasers based on the feedback mechanisms of the photonic bandgap and surface plasmon polaritons, respectively, have been successfully demonstrated. More recently, nanolasers employing new mechanisms of light confinement, including parity–time symmetry lasers, photonic topological insulator lasers, and bound states in the continuum lasers, have been developed. Here, the operational mechanisms, optical characterizations, and practical applications of these nanolasers based on recent research results are outlined. Their scientific and engineering challenges are also discussed.
Recent progress of five representative nanolasers, including photonic crystal lasers, plasmonic lasers, parity–time symmetry lasers, photonic topological insulator lasers, and bound states in the continuum lasers, is reviewed in terms of their operational principles, optical properties, and practical applications. The future perspectives and challenges of these nanolasers are also discussed.
Abstract
The study of topological phases of light underpins a promising paradigm for engineering disorder-immune compact photonic devices with unusual properties. Combined with an optical gain, ...topological photonic structures provide a novel platform for micro- and nanoscale lasers, which could benefit from nontrivial band topology and spatially localized gap states. Here, we propose and demonstrate experimentally active nanophotonic topological cavities incorporating III–V semiconductor quantum wells as a gain medium in the structure. We observe room-temperature lasing with a narrow spectrum, high coherence, and threshold behaviour. The emitted beam hosts a singularity encoded by a triade cavity mode that resides in the bandgap of two interfaced valley-Hall periodic photonic lattices with opposite parity breaking. Our findings make a step towards topologically controlled ultrasmall light sources with nontrivial radiation characteristics.
Harvesting energy from natural resources is of significant interest because of their abundance and sustainability. Seawater is the most abundant natural resource on earth, covering two‐thirds of the ...surface. The rechargeable seawater battery is a new energy storage platform that enables interconversion of electrical energy and chemical energy by tapping into seawater as an infinite medium. Here, an overview of the research and development activities of seawater batteries toward practical applications is presented. Seawater batteries consist of anode and cathode compartments that are separated by a Na‐ion conducting membrane, which allows only Na+ ion transport between the two electrodes. The roles and drawbacks of the three key components, as well as the development concept and operation principles of the batteries on the basis of previous reports are covered. Moreover, the prototype manufacturing lines for mass production and automation, and potential applications, particularly in marine environments are introduced. Highlighting the importance of engineering the cell components, as well as optimizing the system level for a particular application and thereby successful market entry, the key issues to be resolved are discussed, so that the seawater battery can emerge as a promising alternative to existing rechargeable batteries.
Rechargeable seawater batteries tap into earth‐abundant natural seawater as the active material to transform between electrical energy and chemical energy. The progress, challenges, and prospects of seawater batteries for practical applications are summarized.
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Poor water solubility and poor bioavailability are problems with many pharmaceuticals. Increasing surface area by micronization is an effective strategy to overcome these problems, ...but conventional techniques often utilize solvents and harsh processing, which restricts their use. Newer, green technologies, such as supercritical fluid (SCF)-assisted particle formation, can produce solvent-free products under relatively mild conditions, offering many advantages over conventional methods. The antisolvent properties of the SCFs used for microparticle and nanoparticle formation have generated great interest in recent years, because the kinetics of the precipitation process and morphologies of the particles can be accurately controlled. The characteristics of the supercritical antisolvent (SAS) technique make it an ideal tool for enhancing the solubility and bioavailability of poorly water-soluble drugs. This review article focuses on SCFs and their properties, as well as the fundamentals of overcoming poorly water-soluble drug properties by micronization, crystal morphology control, and formation of composite solid dispersion nanoparticles with polymers and/or surfactants. This article also presents an overview of the main aspects of the SAS-assisted particle precipitation process, its mechanism, and parameters, as well as our own experiences, recent advances, and trends in development.
Objectives Pharmaceutical cocrystals are new solid forms with physicochemical properties that appear promising for drug product development. However, the in‐vivo bioavailability of cocrystals has ...rarely been addressed. The cocrystal of indomethacin (IND), a Biopharmaceutical Classification System class II drug, with saccharin (SAC) has been shown to have higher solubility than IND at all pH. In this study, we aimed to evaluate the in‐vitro dissolution and in‐vivo bioavailability of IND–SAC cocrystals in comparison with IND in a physical mixture and the marketed product Indomee®.
Methods Scale‐up of the cocrystals was undertaken using cooling batch crystallisation without seeding. The chemical and physical purity of the up‐scaled material was verified using high‐performance liquid chromatography, differential scanning calorimetry and powder X‐ray diffraction. The IND–SAC cocrystals and IND plus SAC were mixed with lactose and the formulations were placed into gelatin capsules. In‐vitro dissolution studies were then performed using the rotating basket dissolution method. The intrinsic dissolution rate of IND and IND–SAC cocrystals was also determined. Finally, a bioavailability study for the formulations was conducted in beagle dogs. The plasma samples were analysed using high‐performance liquid chromatography and the pharmacokinetic data were analysed using standard methodologies.
Key findings The bulk cocrystals (i.e. scaled‐up material) were chemically and physically pure. The in‐vitro dissolution rate of the cocrystals was higher than that of IND and similar to that of Indomee® at pH 7.4 and pH 1.2. The in‐vivo bioavailability of the IND–SAC cocrystals in dogs was significantly higher (ANOVA, P < 0.05) than that of IND but not significantly different from Indomee® (ANOVA, P > 0.05).
Conclusions The study indicates that the improved aqueous solubility of the cocrystals leads to improved bioavailability of IND. Thus, the cocrystals are a viable alternative solid form that can improve the dissolution rate and bioavailability of poorly soluble drugs.
Summary
Low‐grade inflammation of the intestine results in metabolic dysfunction, in which dysbiosis of the gut microbiota is intimately involved. Dietary fibre induces prebiotic effects that may ...restore imbalances in the gut microbiota; however, no clinical trials have been reported in patients with metabolic diseases. Here, six obese subjects with type 2 diabetes and/or hypertension were assigned to a strict vegetarian diet (SVD) for 1 month, and blood biomarkers of glucose and lipid metabolisms, faecal microbiota using 454‐pyrosequencing of 16S ribosomal RNA genes, faecal lipocalin‐2 and short‐chain fatty acids were monitored. An SVD reduced body weight and the concentrations of triglycerides, total cholesterol, low‐density lipoprotein cholesterol and haemoglobin A1c, and improved fasting glucose and postprandial glucose levels. An SVD reduced the Firmicutes‐to‐Bacteroidetes ratio in the gut microbiota, but did not alter enterotypes. An SVD led to a decrease in the pathobionts such as the Enterobacteriaceae and an increase in commensal microbes such as Bacteroides fragilis and Clostridium species belonging to clusters XIVa and IV, resulting in reduced intestinal lipocalin‐2 and short‐chain fatty acids levels. This study underscores the benefits of dietary fibre for improving the risk factors of metabolic diseases and shows that increased fibre intake reduces gut inflammation by changing the gut microbiota.
Although counter-intuitive features have been observed in non-Hermitian optical systems based on micrometre-sized cavities, the achievement of a simplified but unambiguous approach to enable the ...efficient access of exceptional points (EPs) and the phase transition to desired lasing modes remains a challenge, particularly in wavelength-scale coupled cavities. Here, we demonstrate coupled photonic-crystal (PhC) nanolasers with asymmetric optical gains, and observe the phase transition of lasing modes at EPs through tuning of the area of graphene cover on one PhC cavity and systematic scanning photoluminescence measurements. As the gain contrast between the two identical PhC cavities exceeds the intercavity coupling, the phase transition occurs from the bonding/anti-bonding lasing modes to the single-amplifying lasing mode, which is confirmed by the experimental measurement of the mode images and the theoretical modelling of coupled cavities with asymmetric gains. In addition, we demonstrate active tuning of EPs by controlling the optical loss of graphene through electrical gating.
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