Radiative Coupling Research Articles

Electromagnetic Band Gap Based Via-less Jeans Patch Antenna for 5.5GHz WiMAX Application

Wearable electronics have gained opportunities in recent years, and the last decade has been evidence of this growth in Wireless Body Area Networks (WBAN). They meet the criteria for personalizing healthcare, communication, patient monitoring, tracking, and rescue operations. The main challenge for the WBAN is to handle the radiator's coupling with the human body. An artificially generated Electromagnetic Band Gap (EBG) structure was designed and used in this work to improve the performance of a microstrip patch antenna. A jeans-based microstrip patch antenna with an EBG surface demonstrated to enhance the performance for 5.5 GHz WiMAX application. The use of an EBG surface increases return loss by 20%, with a reasonable bandwidth of 0.528 GHz (5.271 GHz to 5.749 GHz) at the resonance frequency of 5.5 GHz. The EBG surface improved the Voltage Standing Wave Ratio (VSWR) by 60%. A three-layered human body tissue model is also used for on-body measurements to determine the performance of an EBG-based antenna. The presence of human tissues generally reduces performance and shifts the resonance, but the shifting in this work with the simplified EBG structure and adequate gain and VSWR is only 2.6 percent.

Strong Coupling in Diurnal Variations of Clouds, Radiation, Winds, and Precipitation during the East Asian Summer Monsoon

Abstract This study investigates the diurnal cycles of convective activities and low-level winds with emphasis on their interactions during the East Asian summer monsoon. We categorize atmospheric convection states using satellite-derived cloud regimes and group southerly monsoon flows with different characteristics of diurnal cycles, and found that they are closely related to each other. Over South China, deep convection and associated cirrus anvils produce a strongly negative shortwave cloud radiative effect and induce anomalous cooling in the ABL in the daytime, which reduces the diurnal amplitude of monsoon flows during the night that follows. Conversely, a fair-weather state in the daytime leads to an anomalously warm ABL that enhances the subsequent nighttime acceleration of the monsoon southerlies. The dominant cloud regimes in the daytime over South China are closely related to whether the organized deep convection over the Yun-Gui Plateau (southeast of the Tibetan Plateau) propagates eastward during the preceding night. Such a precursor of clouds/convection governing wind diurnal amplitude indicates a possible predictability of monsoon diurnal cycles over South China. Further analyses show that the cloud regimes and induced monsoon diurnal cycles over South China can regulate the moist convection over the downstream region (central China) through modulating moisture transport and convergence. Therefore, the observational statistics of this study reveal a strong coupling of clouds, radiation, winds, and precipitation at the diurnal time scale over the summer monsoon regions, in which the cloud radiative effects of atmospheric convection can strongly regulate the diurnal variations of low-level winds that further influence precipitation downstream.

Endovenous laser coagulation of varicose veins: evolution continues

The article discusses the evolution of the endovenous laser ablation technique for the treatment of varicose vein disease of lower extremities. The history of studies aimed at improving the endovenous laser ablation is provided. The authors described the features of endovenous laser ablation with wavelengths from λ = 0.445 to 1.94 µm, alongside with edge- and radial-emitting working fibers, as well as fibers with radiation absorption at its distal end. The physical and biophysical mechanisms of the most popular to-date method for outpatient treatment of varicose vein disease of lower extremities are reviewed. The propagation process of laser radiation in the scattering medium is described, and the important role of the radiation scattering effect on the depth of its penetration into biological tissues is shown. The processes that take place during endovenous laser ablation are considered. The difference in physical processes that take place during the use of laser radiation mainly absorbed by hemoglobin (hemoglobin-absorbed range) and by water (water-absorbed range) is described. Expedience of simulating the processes that take place during endovenous laser ablation with the use of blood plasma has been substantiated. The blood plasma simulation demonstrated the decisive action of laser-induced boiling on thermal damage to the vein wall, which causes its fibrous transformation. It has been shown that the use of radial-emitting fibres during intense boiling generates steam bubbles around the site of radiation coupling. The contents of such steam bubbles do not absorb radiation, which thus reaches the venous wall, causing its symmetrical thermal damage. The advantages of using water-absorbing radiation with a wavelength of λ = 1.94 µm in conjunction with a radial-emitting fibre have been substantiated.

Dark and bright modes, and their coherent control in dipolar metasurface bilayers

The authors derive a semianalytical model describing the reflection and absorption spectra of dipolar bilayer metasurfaces, showing how radiative coupling between the layers can result in the formation of nonradiative dark modes which can contribute significantly to the optical response of the system. The ability to vary the reflection and absorption spectra of such bilayers by changing the material and geometrical parameters, and to selectively excite the modes by adjusting the phase between two counter-propagating normally incident fields, promises numerous applications.

Meta-Atoms with Toroidal Topology for Strongly Resonant Responses

A conductive meta-atom of toroidal topology is studied both theoretically and experimentally, demonstrating a sharp and highly controllable resonant response. Simulations are performed both for a free-space periodic metasurface and a pair of meta-atoms inserted within a rectangular metallic waveguide. A quasi-dark state with controllable radiative coupling is supported, allowing to tune the linewidth (quality factor) and lineshape of the supported resonance via the appropriate geometric parameters. By conducting a rigorous multipole analysis, we find that despite the strong toroidal dipole moment, it is the residual electric dipole moment that dictates the electromagnetic response. Subsequently, the structure is fabricated with 3D printing and coated with silver paste. Importantly, the structure is planar, consists of a single metallization layer and does not require a substrate when neighboring meta-atoms are touching, resulting in a practical, thin and potentially low-loss system. Measurements are performed in the 5 GHz regime with a vector network analyzer and a good agreement with simulations is demonstrated.

Reflection of two-dimensional surface polaritons by metallic nano-plates on atomically thin crystals

Abstract Owning to their unusual optical properties, such as electrical tunability and strong spatial confinement, two-dimensional surface polaritons (2DSPs) hold great promise for deep sub-wavelength manipulation of light in a reduced low-dimensional space. Control of 2DSPs is possible by using their interaction with a boundary between two media, similar to how light behaves in three-dimensional (3D) space. The understanding of the interaction in the 2D case is still in its early stages, unlike the 3D case, as in-depth investigations are only available in a few cases including the interaction of 2DSPs with structured 2D crystals. Here, we extend the scope of our understanding to the interaction of 2DSPs with metallic nano-plates on 2D crystals, focusing on the reflection of 2DSPs. Through our rigorous model, we reveal that, for strongly confined 2DSPs having much larger momentum than free space photons, the interaction results in almost total internal reflection of 2DSPs as the radiative coupling of the 2DSPs to free space is negligible. We also find that the reflection involves an anomalous phase shift dependent on the thickness of the nano-plate, due to the temporary storing of electromagnetic energy in the evanescent waves induced near the edge of the nano-plate. Our theory predicts that the phase shift saturates to an anomalous value, 0.885π, as the nano-plate becomes thicker. Our work provides a detailed understanding of how to manipulate the 2DSPs by using one of the simplest nanostructures, essential for the further development of nanostructure-integrated low-dimensional devices for polariton optics.

Collective super- and subradiant dynamics between distant optical quantum emitters.

Photon emission is the hallmark of light-matter interaction and the foundation of photonic quantum science, enabling advanced sources for quantum communication and computing. Although single-emitter radiation can be tailored by the photonic environment, the introduction of multiple emitters extends this picture. A fundamental challenge, however, is that the radiative dipole-dipole coupling rapidly decays with spatial separation, typically within a fraction of the optical wavelength. We realize distant dipole-dipole radiative coupling with pairs of solid-state optical quantum emitters embedded in a nanophotonic waveguide. We dynamically probe the collective response and identify both super- and subradiant emission as well as means to control the dynamics by proper excitation techniques. Our work constitutes a foundational step toward multiemitter applications for scalable quantum-information processing.

Nonlocal Ventilating Metasurfaces

A traditional metasurface is composed of metaunits that are elaborately designed to provide a precise local response, and these metaunits also inevitably impact mutual radiation from each other, affecting the global response of the metasurface. Beyond those nonlocal metasurfaces that utilize such radiation coupling to promote efficiency in wave manipulation, in this study the coupling effect also serves as a powerful tool for engineering the spectrum, showcased by an acoustic open metasurface that allows airflow while blocking sound in a dramatically extended frequency band. This finding offers an efficient approach for broadband wave manipulation in a hybrid nonlocal manner.

On the Interplay between Desert Dust and Meteorology Based on WRF-Chem Simulations and Remote Sensing Observations in the Mediterranean Basin

In this study, we investigate a series of Saharan dust outbreaks toward the Mediterranean basin that occurred in late June 2021. In particular, we analyze the effect of mineral dust aerosols on radiation and cloud properties (direct, semi-direct and indirect effects), and in turn, on meteorological parameters. This is achieved by running the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) over a domain covering North Africa and the Central Mediterranean Basin. The simulations were configured using a gradual coupling strategy between the GOCART aerosol model and the Goddard radiation and microphysics schemes available in the WRF-Chem package. A preliminary evaluation of the model performances was conducted in order to verify its capability to correctly reproduce the amount of mineral dust loaded into the atmosphere within the spatial domain considered. To this purpose, we used a suite of experimental data from ground- and space-based remote sensing measurements. This comparison highlighted a model over-estimation of aerosol optical properties to the order of 20%. The evaluation of the desert dust impact on the radiation budget, achieved by comparing the uncoupled and the fully coupled (aerosol–radiation–clouds) simulation, shows that mineral dust induces a net (shortwave–longwave) cooling effect to the order of −10 W m−2. If we consider the net dust radiative forcing, the presence of dust particles induces a small cooling effect at the top of the atmosphere (−1.2 W m−2) and a stronger cooling at the surface (−14.2 W m−2). At the same time, analysis of the perturbation on the surface energy budget yields a reduction of −7 W m−2 when considering the FULL-coupled simulation, a positive perturbation of +3 W m−2 when only considering microphysics coupling and −10.4 W m−2 when only considering radiation coupling. This last result indicates a sort of “superposition” of direct, indirect and semi-direct effects of dust on the radiation budget. This study shows that the presence of dust aerosols significantly influences radiative and cloud properties and specifically the surface energy budget. This suggests (i) that dust effects should be considered in climate models in order to increase the accuracy of climate predictions over the Mediterranean region and (ii) the necessity of performing fully coupled simulations including aerosols and their effects on meteorology at a regional scale.

Influence of high-frequency magnetic fields on the noise behavior of CMS 2S module prototypes

For the CMS tracker Phase-2 upgrade new modules with silicon strip sensors are being developed.Each module features a Service Hybrid (SEH), which is responsible for the distribution of low voltages to the module components using a two-stage DC-DC conversion scheme.For modules equipped with the latest generation of SEHs an increase in module noise has been observed.A setup for inducing radiative noise with external magnetic fields that are frequency- and location-dependent is presented.Measurements carried out on modules from different prototyping phases show that the sensitivity is similar across generations, which indicates that radiative coupling into the sensor or readout electronics is not responsible for the observed noise increase.

Two-Photon Laser Lithography of Functional Microstructures of Integrated Photonics: Waveguides, Microcavities, and Prism Input/Output Adapters of Optical Radiation

The development and optimization of methods for creating functional elements of micron and sub-micron sizes for photonic integrated circuits is one of the main tasks of nanophotonics. Two-photon laser lithography is actively developing now to form three-dimensional structures with subwave resolution. Results of this development are reported and it is shown that the use of optimized lithography schemes, the spatial filtering of laser beam used, and the introduction of laser dyes into polymer lead to the formation of optically homogeneous high-quality bulk microstructures with characteristic features down to 300 nm with necessary functional properties. The capabilities of optimized two-photon laser lithography are demonstrated by examples of ring microcavities and optical waveguides with prism input/output adapters located above a substrate. Optical losses upon the coupling of 405-nm radiation into a waveguide using a printed prism adapter was no more than 1.25 dB.

Probe Design and Source Reconstruction for Near-Field Scanning and Modeling

This paper elaborates the near-field scanning and modeling technique developed for electromagnetic interference (EMI) analysis. The technique has been increasingly deployed in many R&D labs of universities and testing centers of industry companies due to its advantages in terms of time and cost, comparing with conventional EMI measurement methods. The major research works related to the near-field scanning and modeling are probe design and source reconstruction method (SRM). In this article, the working principle of electric and magnetic probes are firstly introduced. Probe parameters including calibration factor, electric center, sensitivity, spatial resolution and bandwidth are discussed. Next, the equivalent radiation source modeling approach is presented. Through SRM, a complex and unknown EMI source is substituted with the simplified equivalent radiation source based on the electromagnetic fields measured by magnetic and/or electric probes. The phaseless SRM is thereafter discussed for addressing the limitations in conventional SRM and its applications prove that the near-field scanning and modeling technique can effectively predict EMI far-field radiation and near-field coupling.

The Influence of Greenhouse Effect on Earth’s Atmosphere Based on Artificial Intelligence

Greenhouse gases absorb and release a large amount of ground thermal radiation, and modify part of the energy between the earth and the atmosphere, so that it has a greenhouse effect. It is the main cause of global warming and climate anomaly caused by modern human activities. In order to solve the shortcomings of the existing research on the impact of greenhouse effect on the Earth’s atmosphere, this paper briefly introduces the numerical methods of radiation and heat conduction coupling, the components of the Earth’s atmosphere, and the sources and sinks of greenhouse gases. The calculation and analysis of spectral absorption coefficient and the configuration of super parameters of depth learning model are discussed. A numerical simulation of carbon dioxide concentration based on depth learning is constructed and the C02 concentration profile is calculated using the C02 statistical inversion flow of principal component analysis. The calculated temperatures of the standard atmosphere and the standard atmosphere with the carbon dioxide concentration doubled were compared. The data showed that the temperature in the upper stratosphere rose to 58.

Influence of radiation coupling effect on polarization characteristics of targets

The predecessor of China Optics was China Optics and Applied Optics Digest, which was founded in 1985. At that time, it was the only retrieval journal in the field of optics in China. At the end of 2008, China Optics and Applied Optics Digest was renamed

The importance of accurately modelling soot and radiation coupling in laminar and laboratory-scale turbulent diffusion flames

Ultrafine and highly light absorbing soot particles have been known to be harmful to human health and a major climate forcer. Understanding the mechanisms of soot formation and developing reliable and robust soot models are essential to design efficient and clean combustion systems. Thermal radiation is often the dominant heat transfer mode in both turbulent and laminar flames and affects soot formation through its influence on temperature. Significant progress has been made in modelling soot formation, thermal radiation transfer, and turbulence radiation interaction in hydrocarbon flames over the last three decades. However, the optically thin approximation has still been used to simplify thermal radiation transfer modelling and turbulence radiation interaction has often been neglected in soot formation modelling without proper justification. In this paper, soot models developed for laminar and laboratory scale turbulent jet diffusion flames, non-gray radiative heat transfer models, and turbulence radiation interaction models are reviewed. The aim of this review is to highlight the importance of thermal radiation heat transfer in both laminar and turbulent diffusion flames and turbulence radiation interaction in turbulent jet diffusion flames. Use of the optically thin approximation is often not justified even in laminar diffusion flames. This is particularly true in diffusion flames at elevated pressures or microgravity. Although the prediction of soot in both laminar and turbulent flames is primarily influenced by soot kinetic model, it is also significantly affected by aerosol dynamic model, thermal radiation heat transfer model, and turbulence radiation interaction model. It is important to accurately model soot aerosol dynamics and non-gray thermal radiation transfer in laminar diffusion flames and additionally to adequately model turbulence radiation interaction in turbulent flames for the purpose of validating reaction mechanisms and soot kinetic models.

Astraeus VII: the environmental-dependent assembly of galaxies in the Epoch of Reionization

ABSTRACT Using the astraeus (seminumerical rAdiative tranSfer coupling of galaxy formaTion and Reionization in N-body dark matter simUlationS) framework, we explore the impact of environmental density and radiative feedback on the assembly of galaxies and their host haloes during the Epoch of Reionization. The astraeus framework allows us to study the evolution of galaxies with masses ($10^{8.2}\,\rm M_\odot \lt M_{\rm h}\lt 10^{13}\,\rm M_\odot$) in a wide variety of environment [−0.5 < log (1 + δ) < 1.3 averaged over (2 cMpc)3]. We find that: (i) there exists a mass- and redshift- dependent ‘characteristic’ environment [${\rm log}\, (1+\delta _a(M_{\rm h}, z)) = 0.021\times (M_{\rm h}/\rm M_\odot)^{0.16} + 0.07 z -1.12$, up to $z$ ∼ 10] at which galaxies are most efficient at accreting dark matter, e.g at a rate of $0.2{{\ \rm per\ cent}}$ of their mass every Myr at $z$ = 5; (ii) the number of minor and major mergers and their contributions to the dark matter assembly increases with halo mass at all redshifts and is mostly independent of the environment; (iii) at $z$ = 5 minor mergers contribute slightly more (by up to $\sim 10{{\ \rm per\ cent}}$) to the dark matter assembly while for the stellar assembly, major mergers dominate the contribution from minor mergers for $M_{\rm h}\lesssim 10^{11.5}\rm\, M_\odot$ galaxies; (iv) radiative feedback quenches star formation more in low-mass galaxies ($M_{\rm h}\lesssim 10^{9.5}\rm\, M_\odot$) in over-dense environments [log(1 + δ) > 0.5]; dominated by their major branch, this yields star formation histories biased towards older ages with a slower redshift evolution.

A Novel Approach to Open “Dead Space” and Modify Interfacial Features of Carbon Nanotube Assemblies by a Microwave Shock

AbstractDespite 30‐year development of carbon nanotube (CNT) based materials, harnessing the outstanding nanoscale properties of individual CNT for macroscale applications remains challenging. High specific surface area, a crucial feature of CNTs, often suffers from the formation of tightly packed bundles with inaccessible “dead space”. Herein, a novel “microwave shock” approach to open the “dead space” trapped within bundles is reported. Employing N2 ambient during microwave irradiation, CNT bundles undergo an efficient structural alteration and interfacial modification simultaneously due to the strong radiative coupling, while the graphitic structure remains undamaged. In this way, a 15‐fold increase (from 42 to 648 m2 g−1) in the interstitial surface area as well as the lithiophilic functionalization (≈1 atom% nitrogen doping) are achieved without the degradation of other properties. Furthermore, to highlight the merits of this microwave shock process, the treated CNT films are applied as a host material for the anode in a lithium metal battery and demonstrate the suppression of dendritic lithium growth and improve cycling stability. This microwave shock approach provides an efficient avenue to modify nanocarbon‐based materials for further applications.

The Schott energy and the reactive energy in electromagnetic radiation and mutual coupling

In the proposed theory for analyzing the electromagnetic radiation and mutual couplings in vacuum, the electromagnetic energy associated with a source is separated into three parts: a Coulomb-velocity energy, a radiative energy and a macroscopic Schott energy. When the sources disappear, the Coulomb-velocity energy disappears simultaneously; a short time later, the total macroscopic Schott energy becomes zero, while the radiative energy keeps propagating and the total radiative energy becomes constant. By applying the Liénard-Wiechert potentials to a moving charge, this paper illustrates that the macroscopic Schott energy corresponds to the Schott energy in the charged particle theory.

Photonic crystals umbrella for thermal desalination: simulation study

For sustainable water desalination, there is a worldwide push towards solar thermal desalination with the objective to limit the amount of consumed energy in other desalination technologies and maximize the resulting freshwater from saline water. Here, we demonstrate a photonic crystals solar umbrella that covers the saline water surface, demanding to absorb all the incident electromagnetic wave and remit it as greater wavelengths in the range of mid-infrared (MIR) to be highly absorbed and localized close to the water surface. The temperature of the saline water with a refractive index of 1.3326 is reached to 45^circ mathrm{C} after one hour of illumination with the incident power intensity equal 680 (mathrm{w}/{mathrm{m}}^{2}). Hence, by adding one-dimensional PCs the surface temperature is reached 77^circ mathrm{C}. Also, by adding 2D PCs to allow the vapor to flow up through the pores of the structure with the diameter of the pore equal to 500 nm, the surface temperature is reached 100^circ mathrm{C} after three hour of illumination. Thus, the effective use of electromagnetic waves and warmth localization at the surface of saline water is accomplished by radiative coupling with the effect of 2D PCs. We design the considered structure by using COMSOL multiphysics which based on the finite element method (FEM).

Simulation and Measurement of an Interaction Structure With Distributed Radiation Coupling Circuit for a High-Power Ku-Band Gyro-TWT

Design and measurement of a distributed radiation coupling (DRC) circuit for the Ku -band TE11-mode gyrotron traveling wave tube (gyro-TWT) amplifier are presented. Different from the dielectric-loaded (DL) waveguide, the proposed DRC circuit can suppress the parasitic modes by achieving sufficient radiation coupling losses. It has the merit of lowering the microwave power loss density, which can improve the tube stability and average power-handling capability. Based on this proposed DRC circuit, a Ku -band TE11-mode gyro-TWT was designed and the particle-in-cell (PIC) simulation shows it can obtain a saturated output power of over 150 kW from 15.3 to 17.2 GHz for an electron beam with a velocity spread of 4.35%. As a comparison, the maximum average microwave power loss density is only 20% of the DL circuit under the same operating parameters. For verification, a DRC circuit was manufactured and cold tested. The maximum deviation between the measured results and our analysis is within 10%.