Bioinspired polylactic acid/polyethylene glycol @ silicon dioxide microfibrous tarpaulin with dual-layer heterogeneous structure for enhanced daytime radiative cooling.

Fibrous tarpaulin serves as the core barrier that protects goods, people, or areas from the adverse impacts of the external environment, such as rain, dust, and sunlight. However, conventional tarpaulins exhibit inadequate mechanical properties, a low solar reflectance, and are susceptible to pollution. To address these issues, a bioinspired polylactic acid/polyethylene glycol @silicon dioxide (PLA/PEG@SiO2) microfibrous tarpaulin with a dual-layer heterogeneous structure was fabricated via in-situ drafting melt-blowing combined with thermal bonding, inspired by the layered structure of shells. This bioinspired dual-layer heterogeneous structure, with an adjustable heterodyne angle and SiO2 size gradient, significantly improved the mechanical performance of the PLA/PEG@SiO2 microfibrous tarpaulin, and specifically manifested as an increase in the bursting strength of the sample to 25.5 N. Moreover, PLA/PEG@SiO2 microfibrous tarpaulin demonstrated excellent anti-pollution properties, effectively repelling liquids and dust. Additionally, its radiative cooling efficiency was notably enhanced, achieving a temperature reduction of ~9.8 °C compared with conventional fabrics, with reflectance of ~88.6 % and emissivity of ~98.3 %. These findings suggest that dual-layered PLA/PEG@SiO2 microfibrous tarpaulin with multifunctional capabilities is a promising candidate for radiative cooling in outdoor shelters, wearable cooling devices, and energy-efficient building insulation materials.

Pressure stabilizes ferrous iron in bridgmanite under hydrous deep lower mantle conditions.

Earth's lower mantle is a potential water reservoir. The physical and chemical properties of the region are in part controlled by the Fe3+/ΣFe ratio and total iron content in bridgmanite. However, the water effect on the chemistry of bridgmanite remains unclear. We carry out laser-heated diamond anvil cell experiments under hydrous conditions and observe dominant Fe2+ in bridgmanite (Mg, Fe)SiO3 above 105 GPa under the normal geotherm conditions corresponding to depth > 2300 km, whereas Fe3+-rich bridgmanite is obtained at lower pressures. We further observe FeO in coexistence with hydrous NiAs-type SiO2 under similar conditions, indicating that the stability of ferrous iron is a combined result of H2O effect and high pressure. The stability of ferrous iron in bridgmanite under hydrous conditions would provide an explanation for the nature of the low-shear-velocity anomalies in the deep lower mantle. In addition, entrainment from a hydrous dense layer may influence mantle plume dynamics and contribute to variations in the redox conditions of the mantle.

Iron silicate perovskite and postperovskite in the deep lower mantle.

Ferromagnesian silicates are the dominant constituents of the Earth's mantle, which comprise more than 80% of our planet by volume. To interpret the low shear-velocity anomalies in the lower mantle, we need to construct a reliable transformation diagram of ferromagnesian silicates over a wide pressure-temperature (P-T) range. While MgSiO3 in the perovskite structure has been extensively studied due to its dominance on Earth, phase transformations of iron silicates under the lower mantle conditions remain unresolved. In this study, we have obtained an iron silicate phase in the perovskite (Pv) structure using synthetic fayalite (Fe2SiO4) as the starting material under P-T conditions of the lower mantle. Chemical analyses revealed an unexpectedly high Fe/Si ratio of 1.72(3) for the Pv phase in coexistence with metallic iron particles, indicating incorporation of about 25 mol% Fe2O3 in the Pv phase with an approximate chemical formula (Fe2+0.75Fe3+0.25)(Fe3+0.25Si0.75)O3. We further obtained an iron silicate phase in the postperovskite (PPv) structure above 95 GPa. The calculated curves of compressional (VP) and shear velocity (VS) of iron silicate Pv and PPv as a function of pressure are nearly parallel to those of MgSiO3, respectively. To the best of our knowledge, the iron silicate Pv and PPv are the densest phases among all the reported silicates stable at P-T conditions of the lower mantle. The high ferric iron content in the silicate phase and the spin-crossover of ferric iron at the Si-site above ~55 GPa should be taken into account in order to interpret the seismic observations. Our results would provide crucial information for constraining the geophysical and geochemical models of the lower mantle.

Continuous selenite biotransformation and biofuel production by marine diatom in the presence of fulvic acid.

In this study, the biochemical response of Phaeodactylum tricornutum to varying concentrations of inorganic selenium (Se) was investigated. It was observed that, when combined with fulvic acid, P. tricornutum exhibited enhanced uptake and biotransformation of inorganic Se, as well as increased microalgal lipid biosynthesis. Notably, when subjected to moderate (5 and 10 mg/L) and high (20 and 40 mg/L) concentrations of selenite under fulvic acid treatment, there was a discernible redirection of carbon flux towards lipogenesis and protein biosynthesis from carbohydrates. In addition, the key parameters of microalgae-based biofuels aligned with the necessary criteria outlined in biofuel regulations. Furthermore, the Se removal capabilities of P. tricornutum, assisted by fulvic acid, were coupled with the accumulation of substantial amounts of organic Se, specifically SeCys. These findings present a viable and successful approach to establish a microalgae-based system for Se uptake and biotransformation.

Phellinus linteus activates Treg cells via FAK to promote M2 macrophage polarization in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is the most prevalent malignant tumor worldwide. Within HCC's tumor microenvironment, focal adhesion kinase (FAK) plays a critical role. Regulatory T cells (Treg) modulate the polarization of tumor-associated macrophages , but the relationship between FAK, Treg cells, and macrophages remains underexplored. Phellinus linteus (PL) shows promise as a treatment for HCC due to its pharmacological effects. This study aimed to explore the relationship between FAK and Treg-macrophages and to assess whether PL could exert a protective effect through the FAK process in HCC. Initially, C57BL/6-FAK-/- tumor-bearing mice were utilized to demonstrate that FAK stimulates HCC tumor development. High dosages (200 µM) of FAK and the FAK activator ZINC40099027 led to an increase in Treg (CD4+CD25+) cells, a decrease in M1 macrophages (F4/80+CD16/32+, IL-12, IL-2, iNOS), and an increase in M2 macrophages (F4/80+CD206+, IL-4, IL-10, Arg1, TGF-ß1). Additionally, FAK was found to encourage cell proliferation, migration, invasion, and epithelial-mesenchymal transition while inhibiting apoptosis in HepG2 and SMMC7721 cells. These effects were mediated by the PI3K/AKT1/Janus Kinase (JAK)/ signal transducer and activator of transcription 3 (STAT3), and mitogen-activated protein kinase (p38 MAPK)/Jun N-terminal Kinase (JNK) signaling pathways. Furthermore, PL exhibited a potent antitumor effect in vivo in a dose-dependent manner, reducing FAK, Treg cells, and M2 macrophages, while increasing M1 macrophages. This effect was achieved through the inhibition of the PI3K/AKT/JAK/STAT3, and p38/JNK pathways. Overall, our findings suggest that FAK promotes HCC via Treg cells that polarize macrophages toward the M2 type through specific signaling pathways. PL, acting through FAK, could be a protective therapy against HCC.

Effecting mechanisms of iron-rich sludge on ash fusion characteristics of coal with high ash fusion temperature under reducing atmosphere.

Co-gasification is crucial for large-scale clean conversion of coal and sludge. In this study, the effects of municipal sewage sludge (MSS, Fe2O3:48.11 %) and pharmaceutical sewage sludge (PSS, Fe2O3: 67.80 %) on ash fusion temperature (AFT) of high AFT Xiangyuan coal (XY) were explored using an AFT analysis, X-ray fluorescence spectrometry, X-ray diffraction, scanning electronic microscopy, and thermodynamics FactSage calculation. The results showed that when MSS or PSS ash mass ratios reached 20 % or 16 % (for XY mixtures, the mass ratio of MSS or PSS should be >5.81 wt% or 5.07 wt%), respectively, the AFT met the requirement of liquid-slag discharge for entrained-flow bed gasification. Under a reducing atmosphere (6:4, CO/CO2, volume ratio), Fe2+ destroyed the bridging-oxygen bonds in the network structure and generated low melting-point (MP) hercynite (FeAl2O4). This resulted in the AFT decreases in the XY mixtures with the additions of PSS or MSS. Meanwhile, the high calcium content (CaO: 13.40 %) easily reacted with Al2O3 and SiO2 and formed anorthite (CaAl2SiO8), which inhibited high-MP mullite formation and decreased the mixed XY AFT. With the increasing SS mass ratio, the surface of the ash sample and thermodynamic FactSage calculation were in good agreement with the experimental results.

Safflower Yellow Inhibits Progression of Hepatocellular Carcinoma by Modulating Immunological Tolerance via FAK Pathway.

OBJECTIVE: To explore the anti-tumor effect of safflower yellow (SY) against hepatocellular carcinoma (HCC) and the underlying potential mechanism. METHODS: An in vitro model was established by mixing Luc-Hepa1-6 cells and CD3+CD8+ T cells, followed by adding programmed cell death protein 1 (PD-1) antibody (Anti-mPD-1) with or without SY. The apoptosis was detected by flow cytometry and the level of inflammatory cytokines was determined by enzyme-linked immunosorbent assay. The protein levels of programmed cell death 1 ligand 1 (PD-L1), chemokine ligand (CCL5), C-X-C motif chemokine ligand 10 (CXCL10) were measured by Western blot. An in situ animal model was established in mice followed by treatment with anti-mPD-1 with or without SY. Bioluminescence imaging was monitored with an AniView 100 imaging system. To establish the FAK-overexpressed Luc-Hepa1-6 cells, cells were transfected with adenovirus containing pcDNA3.1-FAK for 48 h. RESULTS: The fluorescence intensity, apoptotic rate, release of inflammatory cytokines, and CCL5/CXCL10 secretion were dramatically facilitated by anti-mPD-1 (P<0.01), accompanied by an inactivation of PD-1/PD-L1 axis, which were extremely further enhanced by SY (P<0.05 or P<0.01). Increased fluorescence intensity, elevated percentage of CD3+CD8+ T cells, facilitated release of inflammatory cytokines, inactivated PD-1/PD-L1 axis, and increased CCL5/CXCL10 secretion were observed in Anti-mPD-1 treated mice (P<0.01), which were markedly enhanced by SY (P<0.05 or P<0.01). Furthermore, the enhanced effects of SY on inhibiting tumor cell growth, facilitating apoptosis and inflammatory cytokine releasing, suppressing the PD-1/PD-L1 axis, and inducing the CCL5/CXCL10 secretion in Anti-mPD-1 treated mixture of Luc-Hepa1-6 cells and CD3+CD8+ T cells were abolished by FAK overexpression (P<0.01). CONCLUSION: SY inhibited the progression of HCC by mediating immunological tolerance through inhibiting FAK.

IL-4-secreting CD40L+ MAIT cells support antibody production in the peripheral blood of Heonch-Schönlein purpura patients.

OBJECTIVE: Here, we explored the phenotype and function of MAIT cells in the peripheral blood of patients with HSP. METHODS: Blood samples from HSP patients and HDs were assessed by flow cytometry and single-cell RNA sequencing to analyze the proportion, phenotype, and function of MAIT cells. Th-cytokines in the serum of HSP patients were analyzed by CBA. IgA in cocultured supernatant was detected by CBA to analyze antibody production by B cells. RESULTS: The percentage of MAIT cells in HSP patients was significantly reduced compared with that in HDs. Genes related to T cell activation and effector were up-regulated in HSP MAIT cells, indicating a more activated phenotype. In addition, HSP MAIT cells displayed a Th2-like profile with the capacity to produce more IL-4 and IL-5, and IL-4 was correlated with IgA levels in the serum of HSP patients. Furthermore, CD40L was up-regulated in HSP MAIT cells, and CD40L+ MAIT cells showed an increased ability to produce IL-4 and to enhance IgA production by B cells. CONCLUSION: Our data demonstrate that MAIT cells in HSP patients exhibit an activated phenotype. The enhanced IL-4 production and CD40L expression of MAIT cells in HSP patients could take part in the pathogenesis of HSP.

A Thermal-Ball-Valve Structure Separator for Highly Safe Lithium-Ion Batteries.

The separator located between the positive and negative electrodes not only provides a lithium-ion transmission channel but also prevents short circuits for direct contact of electrodes. The inferior dimension thermostability of commercial polyolefin separators intensifies the thermal runaway of batteries under abuse such as short circuits, overcharge, and so on. a polyvinylidene fluoride/polyether imide (PVDF/PEI) separator with high thermal stability in which the high thermostable PEI microspheres are evenly dispersed in the PVDF film matrix and also located in the micro holes of the PVDF film is developed. They not only function as strong skeleton that enables the rare shrink of the separator at 200 °C avoiding short circuit but also act as ball valve that blocks the lithium ion transmission channel at 150 °C interrupting the further heat aggregation. Thus, the LiNi0.6 Co0.2 Mn0.2 O2 /Li batteries exhibit high cycle stability of 96.5% capacity retention after 100 cycles at 0.2C and 80°C. Further, the LiNi0.6 Co0.2 Mn0.2 O2 /graphite pouch cells are constructed and deliver good safety performance without smoke release and catching fire after the nail penetration test.

A 110-170 GHz Wideband LNA Design Using the InP Technology for Terahertz Communication Applications.

This paper proposes a low-noise amplifier (LNA) for terahertz communication systems. The amplifier is designed based on 90 nm InP high-electron-mobility transistor (HEMT) technology. In order to achieve high gain of LNA, the proposed amplifier adopts a five-stage amplification structure. At the same time, the use of staggered tuning technology has achieved a large bandwidth of terahertz low-noise amplification. In addition, capacitors are used for interstage isolation, sector lines are used for RF bypass, and Microstrip is used to design matching circuits. The entire LNA circuit was validated using accurate electromagnetic simulation. The simulation results show that at 140 GHz, the small signal gain is 25 dB, the noise figure is 4.4 dB, the input 1 dB compression point is -19 dBm, and the 3 dB bandwidth reaches 60 GHz (110-170 GHz), which validates the effectiveness of the design.

Real-time programmable metasurface for terahertz multifunctional wave front engineering.

Terahertz (THz) technologies have become a focus of research in recent years due to their prominent role in envisioned future communication and sensing systems. One of the key challenges facing the field is the need for tools to enable agile engineering of THz wave fronts. Here, we describe a reconfigurable metasurface based on GaN technology with an array-of-subarrays architecture. This subwavelength-spaced array, under the control of a 1-bit digital coding sequence, can switch between an enormous range of possible configurations, providing facile access to nearly arbitrary wave front control for signals near 0.34 THz. We demonstrate wide-angle beam scanning with 1° of angular precision over 70 GHz of bandwidth, as well as the generation of multi-beam and diffuse wave fronts, with a switching speed up to 100 MHz. This device, offering the ability to rapidly reconfigure a propagating wave front for beam-forming or diffusively scattered wide-angle coverage of a scene, will open new realms of possibilities in sensing, imaging, and networking.

Flexible solar cells based on foldable silicon wafers with blunted edges.

Flexible solar cells have a lot of market potential for application in photovoltaics integrated into buildings and wearable electronics because they are lightweight, shockproof and self-powered. Silicon solar cells have been successfully used in large power plants. However, despite the efforts made for more than 50 years, there has been no notable progress in the development of flexible silicon solar cells because of their rigidity1-4. Here we provide a strategy for fabricating large-scale, foldable silicon wafers and manufacturing flexible solar cells. A textured crystalline silicon wafer always starts to crack at the sharp channels between surface pyramids in the marginal region of the wafer. This fact enabled us to improve the flexibility of silicon wafers by blunting the pyramidal structure in the marginal regions. This edge-blunting technique enables commercial production of large-scale (>240 cm2), high-efficiency (>24%) silicon solar cells that can be rolled similarly to a sheet of paper. The cells retain 100% of their power conversion efficiency after 1,000 side-to-side bending cycles. After being assembled into large (>10,000 cm2) flexible modules, these cells retain 99.62% of their power after thermal cycling between -70 °C and 85 °C for 120 h. Furthermore, they retain 96.03% of their power after 20 min of exposure to air flow when attached to a soft gasbag, which models wind blowing during a violent storm.

Measurements of emissivity and temperature for polarized long-wavelength infrared light from tungsten under simulating tokamak conditions.

Tungsten is regarded as the baseline first wall material in tokamaks. This work provides a polarized method for measuring the emissivity and temperature of the tungsten using an infrared camera and a polarizer under simulating tokamak conditions. In the experiment, a polarizer with an adjustable polarization direction is set up in front of an infrared camera. A rotatable fixture is used to fix the sample and change the angle between the surface and the normal. The sample is rotated from 0° to 80°, and the polarized emissivity first increases and then decreases with increasing rotation angle. The uncertainty in emissivity resulting from this polarized method and non-polarized method is analyzed. To compare the effects of the polarized method and the non-polarized method, the rotation angle is adjusted to 0°, and a fitting model is used to describe the relationship between emissivity and temperature. Errors between the calculated temperature and measured temperature are used as a scale, and the polarized method improves the accuracy of temperature measurement. This polarized method provides a technical way to measure the emissivity and temperature in a tokamak and can be applied in other similar applications.

Dynamic terahertz transmission based on coupling reconfiguration of spoof surface plasmon polaritons.

In this paper, we propose a dynamic transmission structure based on the coupling reconfiguration of spoof surface plasmon polaritons (SSPPs) in a 2D coplanar grating. By embedding a VO2 film into the signal line, the dynamic transmission is realized by reconfiguring the coupling of terahertz waves from quasi-TEM waves to SSPPs. The analysis shows that the transmission can be modulated in almost the entire band of the SSPPs, which further benefits a promising group delay due to the weak dispersion characteristic in the frequency region much lower than the cut-off frequency of SSPPs. In addition, for the dynamic modulation caused by the coupling reconfiguration, only rather a small area of VO2 film is needed to break the robustness of the 2D coplanar grating. Therefore, the coupling reconfiguration mechanism proposed in this paper facilitates the realization of an easily on-chip integrated dynamic SSPPs transmission structure with ultra-large bandwidth, and low group delay time difference. Accordingly, the presented mechanism will play a positive role in promoting the development of terahertz dynamic devices.

Transferable Ga2O3 Membrane for Vertical and Flexible Electronics via One-Step Exfoliation.

Transferable Ga2O3 thin film membrane is desirable for vertical and flexible solar-blind photonics and high-power electronics applications. However, Ga2O3 epitaxially grown on rigid substrates such as sapphire, Si, and SiC hinders its exfoliation due to the strong covalent bond between Ga2O3 and substrates, determining its lateral device configuration and also hardly reaching the ever-increasing demand for wearable and foldable applications. Mica substrate, which has an atomic-level flat surface and high-temperature tolerance, could be a good candidate for the van der Waals (vdW) epitaxy of crystalline Ga2O3 membrane. Beyond that, benefiting from the weak vdW bond between Ga2O3 and mica substrate, in this work, the Ga2O3 membrane is exfoliated and transferred to arbitrary flexible and adhesive tape, allowing for the vertical and flexible electronic configuration. This straightforward exfoliation method is verified to be consistent and reproducible by the transfer and characterization of thick (∼380 nm)/thin (∼95 nm) κ-phase Ga2O3 and conductive n-type ß-Ga2O3. Vertical photodetectors are fabricated based on the exfoliated Ga2O3 membrane, denoting the peak response at ∼250 nm. Through the integration of Ti/Au Ohmic contact and Ni/Ag Schottky contact electrode, the vertical photodetector exhibits self-powered photodetection behavior with a responsivity of 17 mA/W under zero bias. The vdW-bond-assisted exfoliation of the Ga2O3 membrane demonstrated here could provide enormous opportunities in the pursuit of vertical and flexible Ga2O3 electronics.

Understanding Ash Sintering Variation Behaviors of Low-Rank Coals with Municipal Sludge Addition Based on Mineral Interactions.

Co-gasification with coal provides an economically viable way to use sludge. To investigate the effect of municipal sludge (MS) on the sintering behaviors of low-rank coals (LRCs) and their modification mechanisms, the initial sintering temperature (T s) of three LRCs and their mixtures with MS addition were tested by a T s analyzer, an X-ray diffractometer, and FactSage calculation. The results show that the T s values of Xiaolongtan coal (XLT), Xiangyuan coal (XY), and Daliuta coal (DLT) all increase with MS addition. The 9-12% MS mass ratio is suitable during LRC fluidized-bed gasification to mitigate ash-related issues. The T s is closely related to the liquid-phase content or the transmissions of microparticles (e.g., atoms and ions) or blank spots during heating, while the ash fusion temperatures (AFTs) are mainly determined by acid/base ratios. The T s values of high-Fe XLT and XY mixed ashes increased gradually with increasing MS proportion because the sintering mechanisms transferred from liquid phase to solid phase, while for relatively high-Mg DLT ashes, the T s values increased with increasing MS proportions, which might result from the formations of high-melting-point minerals (e.g., Ca3(PO4)2 and Mg2SiO4). The results deepen the understanding of ash sintering behaviors and provide references to alleviate ash-related issues during gasification.

On the formation of hydrogen peroxide in water microdroplets.

Recent reports on the formation of hydrogen peroxide (H2O2) in water microdroplets produced via pneumatic spraying or capillary condensation have garnered significant attention. How covalent bonds in water could break under such mild conditions challenges our textbook understanding of physical chemistry and water. While there is no definitive answer, it has been speculated that ultrahigh electric fields at the air-water interface are responsible for this chemical transformation. Here, we report on our comprehensive experimental investigation of H2O2 formation in (i) water microdroplets sprayed over a range of liquid flow-rates, (shearing) air flow rates, and air composition, and (ii) water microdroplets condensed on hydrophobic substrates formed via hot water or humidifier under controlled air composition. Specifically, we assessed the contributions of the evaporative concentration and shock waves in sprays and the effects of trace O3(g) on the H2O2 formation. Glovebox experiments revealed that the H2O2 formation in water microdroplets was most sensitive to the air-borne ozone (O3) concentration. In the absence of O3(g), we could not detect H2O2(aq) in sprays or condensates (detection limit ≥250 nM). In contrast, microdroplets exposed to atmospherically relevant O3(g) concentration (10-100 ppb) formed 2-30 µM H2O2(aq), increasing with the gas-liquid surface area, mixing, and contact duration. Thus, the water surface area facilitates the O3(g) mass transfer, which is followed by the chemical transformation of O3(aq) into H2O2(aq). These findings should also help us understand the implications of this chemistry in natural and applied contexts.

Understanding Anthracycline Cardiotoxicity From Mitochondrial Aspect.

Anthracyclines, such as doxorubicin, represent one group of chemotherapy drugs with the most cardiotoxicity. Despite that anthracyclines are capable of treating assorted solid tumors and hematological malignancies, the side effect of inducing cardiac dysfunction has hampered their clinical use. Currently, the mechanism underlying anthracycline cardiotoxicity remains obscure. Increasing evidence points to mitochondria, the energy factory of cardiomyocytes, as a major target of anthracyclines. In this review, we will summarize recent findings about mitochondrial mechanism during anthracycline cardiotoxicity. In particular, we will focus on the following aspects: 1) the traditional view about anthracycline-induced reactive oxygen species (ROS), which is produced by mitochondria, but in turn causes mitochondrial injury. 2) Mitochondrial iron-overload and ferroptosis during anthracycline cardiotoxicity. 3) Autophagy, mitophagy and mitochondrial dynamics during anthracycline cardiotoxicity. 4) Anthracycline-induced disruption of cardiac metabolism.

Steering Smith-Purcell radiation angle in a fixed frequency by the Fano-resonant metasurface.

Smith-Purcell radiation (SPR) is a kind of electromagnetic wave radiation that happens when an energetic beam of electrons passes very closely parallel to the surface of a ruled optical diffraction grating. The frequency of radiation waves varies in the upper and lower space of the grating for different electron velocity, satisfying the SPR relationship. In this study, a Fano-resonant metasurface was proposed to steer the direction of the SPR waves at the fixed resonant frequency by changing the velocity of the electron beam without varying the geometric parameters or adding extra coupling structure. The maximum emission power always locates at the resonant frequency by utilizing the integration of the Poynting vector. The relative radiated efficiency can reach to a maximum value of 91% at the frequency of 441 GHz and the efficiency curve has a dip when the direction of SPR is nearly vertical due to the high transmission. There is a great consistence of steering radiation angle from 65 degrees to 107 degrees by altering the velocity of electron beam from 0.6c to 0.95c both in analytical calculation and PIC (particle-in-cell of CST) simulation at terahertz frequencies, where c is the speed of light in vacuum. Furthermore, the destructive interference of Fano resonance between the magnetic mode and the toroidal mode shows the underlying physics of steering SPR in a fixed frequency. Our study indicates that the proposed structure can produce direction-tunable THz radiation waves at resonant frequency by varying the velocity of the electron beam, which is promising for various applications in a compact, tunable, high power millimeter wave and THz wave radiation sources.

Ultra-extraordinary optical transmission induced by cascade coupling of surface plasmon polaritons in composite graphene-dielectric stack.

Surface plasmon polaritons have been extensively studied owing to the promising characteristics of near fields. In this paper, the cascade coupling of graphene surface plasmon polaritons (GSPPs) originating from cascading excitation and multiple coupling within a composite graphene-dielectric stack is presented. GSPPs confined to graphene layers are distributed in the entire stack as waveguide modes. Owing to the near-field enhancement effect and large lifetime of the GSPPs, the terahertz wave-graphene interaction is significantly enhanced, which induces an ultra-extraordinary optical transmission (UEOT) together with the reported negative dynamic conductivity of graphene. Furthermore, owing to cascade coupling, the UEOT exhibits considerable transmission enhancement, up to three orders of magnitude, and frequency and angle selections. Based on the key characteristics of cascade coupling, the mode density and coupling intensity of GSPPs, the dependences of the number of graphene layers in the stack, the thickness of dielectric buffers, and the effective Fermi levels of the graphene on the UEOT are also analyzed. The proposed mechanism can pave the way for using layered plasmonic materials in electric devices, such as amplifiers, sensors, detectors, and modulators.