Superabsorbent having enhanced absorbency of 0.9%NaCl solution was synthesized on one basis of incorporating zwitterionic (sulfobetaine) monomer into the previous monomer mixture, which comprises ionic (AA) and nonion...Superabsorbent having enhanced absorbency of 0.9%NaCl solution was synthesized on one basis of incorporating zwitterionic (sulfobetaine) monomer into the previous monomer mixture, which comprises ionic (AA) and nonionic monomers, and another basis of introducing inorganic salt B. As far as saline absorbency is concerned, introduction of inorganic salt B is more useful than the sulfobetaine monomer.展开更多
Superabsorbents starch grafted sodium polyacrylate was synthesized by inverse suspension polymerization, using toluene as the continuous phase, potassium persulfate as the initiator. The effect of reaction parameters,...Superabsorbents starch grafted sodium polyacrylate was synthesized by inverse suspension polymerization, using toluene as the continuous phase, potassium persulfate as the initiator. The effect of reaction parameters, such as starch pretreatment temperature, neutralization degree of monomer, reaction time and temperature, concentration of initiator, molar ratio of monomer and starch, on water absorbency of the starch grafted polymer was studied. The effects of the last two parameters were investigated by uniform design method, and the prediction equation was obtained.展开更多
Superabsorbents starch grafted sodium polyacrylate was prepared by inverse suspension polymerization, using toluene as the continuous phase, potassium persulfate as the initiator. The effect of suspension parameters, ...Superabsorbents starch grafted sodium polyacrylate was prepared by inverse suspension polymerization, using toluene as the continuous phase, potassium persulfate as the initiator. The effect of suspension parameters, such as volume ratio of continuous phase and dispersed phase, type and dosage of suspending agents, on water absorbency of the starch grafted polymer was studied. Different starch derivatives were also investigated. Superabsorbents made of cationic starch has higher water absorbency than that made of native corn starch.展开更多
The efficacies of different products made from different parts of the stem of different varieties of kenaf grown in Nigeria as oil absorbents were tested. Particle sizes, genotypes and whether mixed or sole stem core ...The efficacies of different products made from different parts of the stem of different varieties of kenaf grown in Nigeria as oil absorbents were tested. Particle sizes, genotypes and whether mixed or sole stem core or bast differed among the treatments. The fibre component sank in water, and so was not buoyant;the core was partially buoyant while the mixed fibre and core was completely buoyant. Sorption capacity was the highest in the ground whole stem (8.16 g oil/g sorbent), which also retained (6.31 g oil/g sorbent) the highest quantity of oil. Sorption and retention of oil were the lowest in the fibre (1.66 and 0.69 g oil/g sorbent, respectively). After the first use, only the ground stem can be used to re-absorb up to 1.97 g oil/g sorbent of used sorbent. A mixture of genotypes was more absorbent than a single genotype. The implications of these findings in absorbency research are discussed.展开更多
High-temperature microwave absorbing materials(MAMs)and structures are increasingly appealing due to their critical role in stealth applications under harsh environments.However,the impedance mismatch caused by increa...High-temperature microwave absorbing materials(MAMs)and structures are increasingly appealing due to their critical role in stealth applications under harsh environments.However,the impedance mismatch caused by increased conduction loss often leads to a significant decline in electromagnetic wave absorp-tion(EMWA)performance at elevated temperatures,which severely restricts their practical application.In this study,we propose a novel approach for efficient electromagnetic wave absorption across a wide temperature range using reduced graphene oxide(RGO)/epoxy resin(EP)metacomposites that integrate both electromagnetic parameters and metamaterial design concepts.Due to the discrete distribution of the units,electromagnetic waves can more easily penetrate the interior of materials,thereby exhibiting stable microwave absorption(MA)performance and impedance-matching characteristics suitable across a wide temperature range.Consequently,exceptional MA properties can be achieved within the tem-perature range from 298 to 473 K.Furthermore,by carefully controlling the structural parameters in RGO metacomposites,both the resonant frequency and effective absorption bandwidth(EAB)can be optimized based on precise manipulation of equivalent electromagnetic parameters.This study not only provides an effective approach for the rational design of MA performance but also offers novel insights into achieving super metamaterials with outstanding performance across a wide temperature spectrum.展开更多
In this paper, we have demonstrated an Er-doped ultrafast laser with a single mode fiber-gradient index multimode fiber-single mode fiber(SMF-GIMF-SMF, SMS) structure as saturable absorber(SA), which can generate not ...In this paper, we have demonstrated an Er-doped ultrafast laser with a single mode fiber-gradient index multimode fiber-single mode fiber(SMF-GIMF-SMF, SMS) structure as saturable absorber(SA), which can generate not only stable single-pulse state, but also special mode-locked pulses with the characteristics of high energy and noisy behaviors at proper pump power and cavity polarization state. In addition, we have deeply investigated the real-time spectral evolutions of the mode-locked pulses through the dispersive Fourier transformation(DFT) technique. It can be found that the pulse regime can actually consist of a lot of small noise pulses with randomly varying intensities. We believe that these results will further enrich the nonlinear dynamical processes in the ultrafast lasers.展开更多
Gels and conductive polymer composites,including hydrogen bonds(HBs),have emerged as promising materials for electro-magnetic wave(EMW)absorption across various applications.However,the relationship between conduction...Gels and conductive polymer composites,including hydrogen bonds(HBs),have emerged as promising materials for electro-magnetic wave(EMW)absorption across various applications.However,the relationship between conduction loss in EMW-absorbing materials and charge transfer in HB remains to be fully understood.In this study,we developed a series of deep eutectic gels to fine-tune the quantity of HB by adjusting the molar ratio of choline chloride(ChCl)and ethylene glycol(EG).Owing to the unique properties of deep eutectic gels,the effects of magnetic loss and polarization loss on EMW attenuation can be disregarded.Our results indicate that the quantity of HB initially increases and then decreases with the introduction of EG,with HB-induced conductive loss following similar pat-terns.At a ChCl and EG molar ratio of 2.4,the gel labeled G22-CE2.4 exhibited the best EMW absorption performance,characterized by an effective absorption bandwidth of 8.50 GHz and a thickness of 2.54 mm.This superior performance is attributed to the synergistic ef-fects of excellent conductive loss and impedance matching generated by the optimal number of HB.This work elucidates the role of HB in dielectric loss for the first time and provides valuable insights into the optimal design of supramolecular polymer absorbers.展开更多
With the booming development of electronic information science and 5G communication technology,electromagnetic radi-ation pollution poses a huge threat and damage to humanity.Developing novel and high-performance elec...With the booming development of electronic information science and 5G communication technology,electromagnetic radi-ation pollution poses a huge threat and damage to humanity.Developing novel and high-performance electromagnetic wave(EMW)ab-sorbers is an effective method to solve the above issue and has attracted the attention of many researchers.As a typical magnetic material,ferrite plays an important role in the design of high-performance EMW absorbers,and related research focuses on diversified synthesis methods,strong absorption performance,and refined microstructure development.Herein,we focus on the synthesis of ferrites and their composites and introduce recent advances in the high-temperature solid-phase method,sol-gel method,chemical coprecipitation method,and solvent thermal method in the preparation of high-performance EMW absorbers.This review aims to help researchers understand the advantages and disadvantages of ferrite-based EMW absorbers fabricated through these methods.It also provides important guidance and reference for researchers to design high-performance EMW absorption materials based on ferrite.展开更多
Cu_(2)ZnSn(S,Se)_(4)(CZTSSe)is considered to be the most potential light-absorbing material to replace CuInGaSe_(2)(CIGS),but the actual photoelectric conversion efficiency of such cells is much lower than that of CIG...Cu_(2)ZnSn(S,Se)_(4)(CZTSSe)is considered to be the most potential light-absorbing material to replace CuInGaSe_(2)(CIGS),but the actual photoelectric conversion efficiency of such cells is much lower than that of CIGS.One of the reasons is the high recombination rate of carriers at the interface.In this paper,in order to reduce the carrier recombination,a new solar cell structure with double absorber layers of Al-doped ZnO(AZO)/intrinsic(i)-ZnO/CdS/CZTS_(x1)Se_(1−x1)(CZTSSe_(1))/CZTS_(x2)Se_(1−x2)(CZTSSe_(2))/Mo was proposed,and the optimal conduction band offsets(CBOs)of CdS/CZTSSe_(1) interface and CZTSSe_(1)/CZTSSe_(2) interface were determined by changing the S ratio in CZTSSe_(1) and CZTSSe_(2),and the effect of thickness of CZTSSe_(1) on the performance of the cell was studied.The efficiencies of the optimized single and double absorber layers reached 17.97%and 23.4%,respectively.Compared with the single absorber layer structure,the proposed structure with double absorber layers has better cell performance.展开更多
Carbon-based foams with a three-dimensional structure can serve as a lightweight template for the rational design and control-lable preparation of metal oxide/carbon-based composite microwave absorption materials.In t...Carbon-based foams with a three-dimensional structure can serve as a lightweight template for the rational design and control-lable preparation of metal oxide/carbon-based composite microwave absorption materials.In this study,a flake-like nickel cobaltate/re-duced graphene oxide/melamine-derived carbon foam(FNC/RGO/MDCF)was successfully fabricated through a combination of solvo-thermal treatment and high-temperature pyrolysis.Results indicated that RGO was evenly distributed in the MDCF skeleton,providing ef-fective support for the load growth of FNC on its surface.Sample S3,the FNC/RGO/MDCF composite prepared by solvothermal method for 16 h,exhibited a minimum reflection loss(RL_(min))of-66.44 dB at a thickness of 2.29 mm.When the thickness was reduced to 1.50 mm,the optimal effective absorption bandwidth was 3.84 GHz.Analysis of the absorption mechanism of FNC/RGO/MDCF revealed that its excellent absorption performance was primarily attributed to the combined effects of conduction loss,multiple reflection,scattering,in-terface polarization,and dipole polarization.展开更多
The increase in the utilization of infrared heat detection technology in military applications necessitates research on composites with improved thermal transmission performance and microwave absorption capabilities.T...The increase in the utilization of infrared heat detection technology in military applications necessitates research on composites with improved thermal transmission performance and microwave absorption capabilities.This study satisfactorily fabricated a series of MoS_(2)/BN-xyz composites(which were characterized by the weight ratio of MoS_(2)to BN,denoted by xy:z)through chemical vapor depos-ition,which resulted in their improved thermal stability and thermal transmission performance.The results show that the remaining mass of MoS_(2)/BN-101 was as high as 69.25wt%at 800℃under air atmosphere,and a temperature difference of 31.7℃was maintained between the surface temperature and the heating source at a heating temperature of 200℃.Furthermore,MoS_(2)/BN-301 exhibited an im-pressive minimum reflection loss value of-32.21 dB at 4.0 mm and a wide effective attenuation bandwidth ranging from 9.32 to 18.00 GHz(8.68 GHz).Therefore,these simplified synthesized MoS_(2)/BN-xyz composites demonstrate great potential as highly efficient con-tenders for the enhancement of microwave absorption performance and thermal conductance.展开更多
The dielectric loss of carbon materials is closely related to the microstructure and the degree of crystallization,and the microstructure modulation of electromagnetic wave absorbing carbon materials is the key to enh...The dielectric loss of carbon materials is closely related to the microstructure and the degree of crystallization,and the microstructure modulation of electromagnetic wave absorbing carbon materials is the key to enhancing absorption properties.In this work,a porous elastic Co@CNF-PDMS composite was prepared by freeze-drying and confined catalysis.The graphitization degree and conductivity loss of carbon nanofibers(CNFs)were regulated by heat treatment temperature and Co catalyst content.The construction of a heterointerface between Co and C enhances the interfacial polarization loss.The Co@CNF-PDMS composite with 4.5 mm achieves the minimum reflection loss(RLmin)of-81.0 dB at 9.9 GHz and RL no higher than-12.1 dB in the whole of the X-band.After applying a load of up to 40% strain and 100 cycles to Co@CNF-PDMS,the dielectric properties of the composite remain stable.With the increase of compression strain,the distribution density of the absorbent increases,and the CNF sheet layer extrusion contact forms a conductive path,which leads to the conductive loss increase,finally,the absorption band moves to a high frequency.The absorption band can be bi-directionally regulated by loading and strain with good stability,which provides a new strategy for the development of intelligent electromagnetic wave absorbing materials.展开更多
In recent years, the research advancements have high-lighted the critical role of the A-site cation in determining the optoelectronic and physicochemical properties of organicinorganic lead halide perovskites. Mixed-c...In recent years, the research advancements have high-lighted the critical role of the A-site cation in determining the optoelectronic and physicochemical properties of organicinorganic lead halide perovskites. Mixed-cation perovskites(MCPs) have been extensively used as absorber thin films in perovskite solar cells(PSCs), achieving high power conversion efficiencies(PCE) over 26%^([1, 2]).展开更多
[Background and purposes]In recent years,there has been growing attention in academia and industry on the development of high-performance electromagnetic wave(EMW)absorbing materials.However,creating lightweight broad...[Background and purposes]In recent years,there has been growing attention in academia and industry on the development of high-performance electromagnetic wave(EMW)absorbing materials.However,creating lightweight broadband absorbers remains a challenge in terms of practical applications.EMW absorbing materials primarily rely on the magnetic loss of magnetic materials and/or the dielectric loss of dielectric materials to convert EMW energy into thermal energy for dissipation.Among various magnetic materials,Fe_(3)O_(4) plays an irreplaceable role in EMW absorption due to its high saturation magnetization,low cost and compatible dielectric loss in the gigahertz frequency range.Nevertheless,the high density,large matching thickness and narrow absorption bandwidth of Fe_(3)O_(4) pose significant challenges for practical applications.In contrast,one-dimensional(1D)structures not only retain the characteristic properties of lightweight,chemical stability and high dielectric loss,but also exhibit anisotropic structures and large aspect ratios.Additionally,researchers have found that the minimum reflection loss(RL)of hollow carbon materials with mesopores is nearly four times that of non-porous hollow carbon materials and nine times that of dense carbon materials.According to Maxwell's EMW theory,composites consisting of Fe_(3)O_(4) and one-dimensional(1D)mesoporous carbon materials can leverage their respective advantages by optimizing the composition and structure of the composites to balance u,and Er,thereby enhancing EMW absorption performance.Additionally,numerous studies have demonstrated that composites composed of multi-component heterostructures significantly enhance the EAB.This enhancement is primarily ascribed to the numerous interface polarization losses generated by the additional heterostructure interfaces,which also improve the overall impedance matching of the composites.In this study,we leverage the advantages of magnetic/carbon composites,one-dimensional(1D)mesoporous carbon and multi-component heterostructures to prepare a composite of 1D mesoporous carbon-coated manganese oxide(Mn_(3)O_(4) and MnO,denoted as Mn_(x)O_(y))embedded with Fe_(3)0_(4) nanoparticles(Mn_(x)O_(y)/C@Fe_(3)O_(4)).This composite was synthesized and its formation mechanism and microstructure were analyzed in detail.At the same time,the influence of this Mn_(x)O_(y)/C@Fe_(3)O_(4) structure on EMW properties and absorbing performance was further discussed.[Methods]Firstly,MnO_(2) nanowires were synthesized by using a simple hydrothermal method.Then,the MnO_(2) nanowires served as templates for the synthesis of MnO_(2)/PDA@Fe^(3+)composites through the in-situ polymerization of dopamine and Fe^(3+)adsorption.Finally,1D mesoporous carbon-coated manganese oxide composite embedded with Fe_(3)O_(4) nanoparticles(Mn_(x)O_(y)/C@Fe_(3)O_(4))composites were obtained after heat treatment at 550℃ in N_(2).The crystal structure of the samples was analyzed using X-ray diffractometer with Cu Ka irradiation.Scanning electron microscopy(SEM)and high-resolution transmission electron microscopy(TEM)were used to observe microstructure and morphology of the samples.Nitrogen sorption measurements were obtained at 77 K on a Quantachrome surface area and pore size analyzer to measure the specific surface area and pore size distribution.XPS analysis was performed on X-ray photoelectron spectrometer with monochromatic Al Ka radiation.Magnetization curves of the samples were recorded with a Quantum Design physical property measurement system(PPMS-9)at room temperature.The electromagnetic parameters of the Mn_(x)O_(y)/C@Fe_(3)O_(4) composites were measured using an Agilent N5230C network analyzer in the frequency range of 2-18 GHz.For electromagentic testing,the Mn,Oy/C@Fe34 composites and paraffin wax were mixed at 50°C according to the mass ratio of 15 wt.%,20 wt.%and 25 wt.%,and pressed in a special mold to make coaxial rings(inner diameter=3.04 mm,outer diameter-7 mm),which were denoted as S-1,S-2 and S-3,respectively.[Results]SEM images illustrate the preparation process of iD mesoporous carbon-coated manganese oxide embedded with Fe3O4 nanoparticles composites(Mn_(x)O_(y)/C@Fe_(3)O_(4)).Most of the manganese oxide(Mn,Oy)was reduced to granular after heat treatment,while the outer carbon layer remains its 1D morphology and the carbon layer is interspersed with Fe_(3)O_(4) nanoparticles.The diffraction peaks of MnO_(2) nanowires align well with the body-centered tetragonal a-MnO2.For the Mn_(x)O_(y)/C@Fe_(3)O_(4) composites,the signals of α-MnO_(2) disappears,followed by the emergence of Mn_(3)O_(4) and three prominent diffraction peaks for the cubic MnO.In addition,four weak diffraction peaks correspond to the magnetite Fe_(3)O_(4),consistent with the HRTEM results.The corresponding nitrogen adsorption-desorption isotherm and pore size distribution curve are presented to further analyze the mesoporous structure of composite.The surface composition and element valence states of the Mn_(x)O_(y)/C@Fe_(3)O_(4) composite were investigated by using XPS.The polarization relaxation processes were analyzed according to the Debye theory which describes the relationship between e'and e".Besides the polarization loss,the contribution of the conduction loss plays an important role for the overall dielectric loss.The magnetization curve of Mn_(x)O_(y)/C@Fe_(3)O_(4) exhibits typical ferromagnetic behavior.The permittivity parameter(Co),defined as Co=u"(u)^(-2)f^(-1) determine the contribution of eddy current effect to magnetic loss.The tand values are all larger than those of tand,for the three samples,indicating that the loss capacity of Mn_(x)O_(y)/C@Fe_(3)O_(4) composites is mainly derived from the dielectric loss.Although tand,is smaller,it plays an important role in improving the impedance matching of Mn_(x)O_(y)/C@Fe_(3)O_(4) composites.When the filler loading is 15 wt.%,the RL of sample S-1 is about-10.0 dB at the thickness of 1.5 mm with narrow EAB.As the filler loading increased to 20 wt.%,the RL of sample S-2 reached-62.0 dB at a thickness of 2.2 mm and the EAB was 6.4 GHz at a small thickness of 1.7 mm.When the filler loading is further increased to 25 wt.%,the microwave absorption performance of sample S3 decreased significantly with a little region of RL<-10.0 dB at the thickness of 5.0 mm.The values of[Zin/Zol of the three samples at thicknesses of 1.5-5.0 mm were calculated.Due to good impedance matching of S-2,the incident EMW can enter the material and then can be dissipated through dipole polarization loss,interface polarization loss,conduction loss,eddy current loss and natural ferromagnetic resonance loss.[Conclusions]1D Mn_(x)O_(y)/C@Fe_(3)O_(4) was synthesized via a process involving the coating of polydopamine,adsorption of Fe(ll)salts and heat treatment,using MnO_(2) nanowires as templates.The multi-component heterostructure of the Mn_(x)O_(y)/C@Fe_(3)O_(4) composite(Mn_(3)O_(4),MnO,Fe_(3)O_(4),and C)enhances the interfacial interactions between the different phases,providing increased interface polarization loss under the action of an alternating electromagnetic field.The numerous defects and terminal groups in the mesoporous carbon provide abundant dipole polarization centers.Additionally,the presence of mesopores reduces the weight of the material while increasing the multiple scattering losses of the electromagnetic waves within the material.The ID carbon structure in the matrix forms a conductive network between adjacent fibers,facilitating electron migration and transition,thereby enhancing conductive loss.The incorporation of magnetic Fe_(3)O_(4) nanoparticles introduces eddy current loss and natural ferromagnetic resonance loss,thus increasing magnetic loss.Moreover,the synergistic effect between dielectric and magnetic losses improves the impedance matching of the material,leading to excellent EMW absorption performance.展开更多
As a representative transition metal dichalcogenides(TMD),NiTe_(2)has an ultra-fast optical response,high carrier mobility,and excellent environmental stability.It has a broad application prospect in the fields of ene...As a representative transition metal dichalcogenides(TMD),NiTe_(2)has an ultra-fast optical response,high carrier mobility,and excellent environmental stability.It has a broad application prospect in the fields of ener-gy,biomedicine,optoelectronic devices,and so on.At present,there have been scant reports on the application of NiTe_(2)in the field of ultrafast photonics.In this work,NiTe_(2)was synthesized by chemical vapor deposition(CVD)and integrated with a tapered optical fiber to achieve mode-locking in an erbium-doped fiber laser(EDFL)and a thu-lium-doped fiber laser(TDFL).The mode-locked EDFL exhibited a pulse width of 678 fs and an output power of 3.92 mW.The pulse width of mode-locked TDFL was estimated to have a pulse width of 694 fs with an output power of 21.64 mW.These results demonstrate that NiTe_(2)is an effective saturable absorber material with potential applica-tions in the field of ultrafast optics.展开更多
In this paper,a conventional soliton(CS)mode-locked erbium-doped fiber(EDF)laser was de-veloped using MAX phase material(MAX-PM)Nb_(4)AlC_(3)as a saturable absorber(SA).First,the liquid phase exfoliation(LPE)method wa...In this paper,a conventional soliton(CS)mode-locked erbium-doped fiber(EDF)laser was de-veloped using MAX phase material(MAX-PM)Nb_(4)AlC_(3)as a saturable absorber(SA).First,the liquid phase exfoliation(LPE)method was utilized to prepare Nb_(4)AlC_(3)nanosheets,and then a piece of tapered fiber was adopted to fabricate Nb_(4)AlC_(3)-SA.It was found that the saturation intensity and modulation depth of the Nb_(4)AlC_(3)-SA are 2.02 MW/cm^(2)and 1.88%.Based on the Nb_(4)AlC_(3)-SA,a conventional soliton(CS)mode-locked EDF laser was achieved.The central wavelength,pulse duration,and pulse repetition rate were found to be 1565.65 nm,615.37 fs,and 24.63 MHz,respectively.The performance is competitive and particularly superior in terms of pulse duration.This study fully confirms that Nb_(4)AlC_(3)possesses marvellous nonlinear saturable absorption properties and opens new possibilities for further research on air-stable ultrafast photon-ic devices.展开更多
In today's era of continuous advancement in materials science,the properties of materials are constantly being enhanced,and their application fields are also expanding continuously.SAF(Super Absorbent Fiber),one s...In today's era of continuous advancement in materials science,the properties of materials are constantly being enhanced,and their application fields are also expanding continuously.SAF(Super Absorbent Fiber),one such material,stands out.Compared to traditional SAP(Super Absorbent Polymer),SAF boasts a unique fibrous form and exceptional performance,presenting broad application prospects.展开更多
Optically transparent microwave absorbers and multi-band stealth have extensive potential applications in military defense and wireless communication fields, and thus have attracted considerable attention. So far,most...Optically transparent microwave absorbers and multi-band stealth have extensive potential applications in military defense and wireless communication fields, and thus have attracted considerable attention. So far,most related work is based on inorganic transparent conductive metasurfaces. In this paper, we proposed and experimentally demonstrated a flexible, broadband and optically transparent microwave absorber using an organic metasurface. The metasurface absorber is composed of a sandwich structure, in which electric resonances and magnetic resonances are induced resulting in broadband absorption. A spraying process was developed to prepare this metasurface absorber. Both simulations and experiment show that this metasurface has broadband microwave absorption and good optical transparency. We further found that by using a multi-layer structure, visible, radar,and infrared stealth(multi-band stealth) can be achieved simultaneously. With the advantages of excellent foldability and low cost, the proposed metasurfaces may have applications in military and wireless communication fields.展开更多
Due to their unique physical properties,nonlinear materials are gradually demonstrating significant potential in the field of optics.Gold nanoparticles supported on carbon black(Au/CB),possessing low loss and high non...Due to their unique physical properties,nonlinear materials are gradually demonstrating significant potential in the field of optics.Gold nanoparticles supported on carbon black(Au/CB),possessing low loss and high nonlinear characteristics,serve as an excellent material for saturable absorber(SA) in ultrafast fiber lasers.In this study,we investigated the performance of Au/CB material and designed an ultrafast fiber laser based on Au/CB SA,successfully observing stable fundamental mode-locking and pulse bunch phenomena.Specifically,when the fiber laser operates in fundamental mode-locking state,the center wavelength of optical spectrum is 1 558.82 nm,with a 3 dB bandwidth of 2.26 nm.Additionally,to investigate the evolution of real-time spectra,the dispersive Fourier transform(DFT) technology is employed.On the other hand,the pulse bunch emitted by the laser is actually composed of numerous random sub-pulses,exhibiting high-energy characteristics.The number of sub-pulses increases with the increase of pump power.These findings contribute to further exploring the properties of Au/CB material and reveal its potential applications in ultrafast optics.展开更多
Metasurfaces,which are two-dimensional arrays of subwavelength elements,enable versatile control of electromagnetic waves,thereby paving the way for advancements in electromagnetic stealth.Electromagnetic stealth aims...Metasurfaces,which are two-dimensional arrays of subwavelength elements,enable versatile control of electromagnetic waves,thereby paving the way for advancements in electromagnetic stealth.Electromagnetic stealth aims to diminish object visibility to radar or other sensors by minimizing their reflection,scattering,or emission of electromagnetic waves.This paper reviews the latest works in microwave electromagnetic stealth devices utilizing metasurfaces,including absorbing,scattering,cloaking and multifunctional stealth techniques.A comprehensive analysis and characterization of these stealth metasurface based devices are presented,focusing on their working principles,performance characteristics,and the associated challenges.Additionally,we explore prospects and opportunities for further research.This paper offers a thorough and upto-date survey of the current status and future directions of this emerging field.展开更多
基金Shanghai Municipal ScienceTechnology fund(No.991211031)Shanghai Municipal Key Discipline Project
文摘Superabsorbent having enhanced absorbency of 0.9%NaCl solution was synthesized on one basis of incorporating zwitterionic (sulfobetaine) monomer into the previous monomer mixture, which comprises ionic (AA) and nonionic monomers, and another basis of introducing inorganic salt B. As far as saline absorbency is concerned, introduction of inorganic salt B is more useful than the sulfobetaine monomer.
文摘Superabsorbents starch grafted sodium polyacrylate was synthesized by inverse suspension polymerization, using toluene as the continuous phase, potassium persulfate as the initiator. The effect of reaction parameters, such as starch pretreatment temperature, neutralization degree of monomer, reaction time and temperature, concentration of initiator, molar ratio of monomer and starch, on water absorbency of the starch grafted polymer was studied. The effects of the last two parameters were investigated by uniform design method, and the prediction equation was obtained.
文摘Superabsorbents starch grafted sodium polyacrylate was prepared by inverse suspension polymerization, using toluene as the continuous phase, potassium persulfate as the initiator. The effect of suspension parameters, such as volume ratio of continuous phase and dispersed phase, type and dosage of suspending agents, on water absorbency of the starch grafted polymer was studied. Different starch derivatives were also investigated. Superabsorbents made of cationic starch has higher water absorbency than that made of native corn starch.
文摘The efficacies of different products made from different parts of the stem of different varieties of kenaf grown in Nigeria as oil absorbents were tested. Particle sizes, genotypes and whether mixed or sole stem core or bast differed among the treatments. The fibre component sank in water, and so was not buoyant;the core was partially buoyant while the mixed fibre and core was completely buoyant. Sorption capacity was the highest in the ground whole stem (8.16 g oil/g sorbent), which also retained (6.31 g oil/g sorbent) the highest quantity of oil. Sorption and retention of oil were the lowest in the fibre (1.66 and 0.69 g oil/g sorbent, respectively). After the first use, only the ground stem can be used to re-absorb up to 1.97 g oil/g sorbent of used sorbent. A mixture of genotypes was more absorbent than a single genotype. The implications of these findings in absorbency research are discussed.
基金supported by the National Nature Science Foundation of China(Nos.22305066 and 52372041).
文摘High-temperature microwave absorbing materials(MAMs)and structures are increasingly appealing due to their critical role in stealth applications under harsh environments.However,the impedance mismatch caused by increased conduction loss often leads to a significant decline in electromagnetic wave absorp-tion(EMWA)performance at elevated temperatures,which severely restricts their practical application.In this study,we propose a novel approach for efficient electromagnetic wave absorption across a wide temperature range using reduced graphene oxide(RGO)/epoxy resin(EP)metacomposites that integrate both electromagnetic parameters and metamaterial design concepts.Due to the discrete distribution of the units,electromagnetic waves can more easily penetrate the interior of materials,thereby exhibiting stable microwave absorption(MA)performance and impedance-matching characteristics suitable across a wide temperature range.Consequently,exceptional MA properties can be achieved within the tem-perature range from 298 to 473 K.Furthermore,by carefully controlling the structural parameters in RGO metacomposites,both the resonant frequency and effective absorption bandwidth(EAB)can be optimized based on precise manipulation of equivalent electromagnetic parameters.This study not only provides an effective approach for the rational design of MA performance but also offers novel insights into achieving super metamaterials with outstanding performance across a wide temperature spectrum.
基金supported by the Guangdong Basic and Applied Basic Research Foundation (No.2023A1515010093)the Shenzhen Fundamental Research Program (Stable Support Plan Program)(Nos.JCYJ20220809170611004, 20231121110828001 and 20231121113641002)the National Taipei University of Technology-Shenzhen University Joint Research Program (No.2024001)。
文摘In this paper, we have demonstrated an Er-doped ultrafast laser with a single mode fiber-gradient index multimode fiber-single mode fiber(SMF-GIMF-SMF, SMS) structure as saturable absorber(SA), which can generate not only stable single-pulse state, but also special mode-locked pulses with the characteristics of high energy and noisy behaviors at proper pump power and cavity polarization state. In addition, we have deeply investigated the real-time spectral evolutions of the mode-locked pulses through the dispersive Fourier transformation(DFT) technique. It can be found that the pulse regime can actually consist of a lot of small noise pulses with randomly varying intensities. We believe that these results will further enrich the nonlinear dynamical processes in the ultrafast lasers.
基金supported by the National Nat-ural Science Foundation of China(Nos.51872238,52074227,and 21806129)the Fundamental Research Funds for the Central Universities,China(Nos.3102018zy045 and 3102019AX11)+2 种基金the Guangdong Basic and Applied Basic Research Foundation,China(No.2024A1515010298)the Natural Science Basic Research Plan in Shaanxi Province of China(Nos.2017JQ5116 and 2020JM-118)the Key Laboratory of Icing and Anti/De-icing of CARDC(No.IADL20220401).
文摘Gels and conductive polymer composites,including hydrogen bonds(HBs),have emerged as promising materials for electro-magnetic wave(EMW)absorption across various applications.However,the relationship between conduction loss in EMW-absorbing materials and charge transfer in HB remains to be fully understood.In this study,we developed a series of deep eutectic gels to fine-tune the quantity of HB by adjusting the molar ratio of choline chloride(ChCl)and ethylene glycol(EG).Owing to the unique properties of deep eutectic gels,the effects of magnetic loss and polarization loss on EMW attenuation can be disregarded.Our results indicate that the quantity of HB initially increases and then decreases with the introduction of EG,with HB-induced conductive loss following similar pat-terns.At a ChCl and EG molar ratio of 2.4,the gel labeled G22-CE2.4 exhibited the best EMW absorption performance,characterized by an effective absorption bandwidth of 8.50 GHz and a thickness of 2.54 mm.This superior performance is attributed to the synergistic ef-fects of excellent conductive loss and impedance matching generated by the optimal number of HB.This work elucidates the role of HB in dielectric loss for the first time and provides valuable insights into the optimal design of supramolecular polymer absorbers.
基金supported by the National Natural Science Foundation of China(No.52377026)Taishan Scholars and Young Experts Program of Shandong Province,China(No.tsqn202103057)the Natural Science Foundation of Shandong Province,China(No.ZR2024ME046).
文摘With the booming development of electronic information science and 5G communication technology,electromagnetic radi-ation pollution poses a huge threat and damage to humanity.Developing novel and high-performance electromagnetic wave(EMW)ab-sorbers is an effective method to solve the above issue and has attracted the attention of many researchers.As a typical magnetic material,ferrite plays an important role in the design of high-performance EMW absorbers,and related research focuses on diversified synthesis methods,strong absorption performance,and refined microstructure development.Herein,we focus on the synthesis of ferrites and their composites and introduce recent advances in the high-temperature solid-phase method,sol-gel method,chemical coprecipitation method,and solvent thermal method in the preparation of high-performance EMW absorbers.This review aims to help researchers understand the advantages and disadvantages of ferrite-based EMW absorbers fabricated through these methods.It also provides important guidance and reference for researchers to design high-performance EMW absorption materials based on ferrite.
基金supported by the Science and Technology Innovation Development Program(No.70304901).
文摘Cu_(2)ZnSn(S,Se)_(4)(CZTSSe)is considered to be the most potential light-absorbing material to replace CuInGaSe_(2)(CIGS),but the actual photoelectric conversion efficiency of such cells is much lower than that of CIGS.One of the reasons is the high recombination rate of carriers at the interface.In this paper,in order to reduce the carrier recombination,a new solar cell structure with double absorber layers of Al-doped ZnO(AZO)/intrinsic(i)-ZnO/CdS/CZTS_(x1)Se_(1−x1)(CZTSSe_(1))/CZTS_(x2)Se_(1−x2)(CZTSSe_(2))/Mo was proposed,and the optimal conduction band offsets(CBOs)of CdS/CZTSSe_(1) interface and CZTSSe_(1)/CZTSSe_(2) interface were determined by changing the S ratio in CZTSSe_(1) and CZTSSe_(2),and the effect of thickness of CZTSSe_(1) on the performance of the cell was studied.The efficiencies of the optimized single and double absorber layers reached 17.97%and 23.4%,respectively.Compared with the single absorber layer structure,the proposed structure with double absorber layers has better cell performance.
基金support of the Key Science Research Project in Colleges and Universities of Anhui Province,China(No.2022AH050813)the Medical Special Cultivation Project of Anhui University of Science and Technology,China(No.YZ2023H2A002).
文摘Carbon-based foams with a three-dimensional structure can serve as a lightweight template for the rational design and control-lable preparation of metal oxide/carbon-based composite microwave absorption materials.In this study,a flake-like nickel cobaltate/re-duced graphene oxide/melamine-derived carbon foam(FNC/RGO/MDCF)was successfully fabricated through a combination of solvo-thermal treatment and high-temperature pyrolysis.Results indicated that RGO was evenly distributed in the MDCF skeleton,providing ef-fective support for the load growth of FNC on its surface.Sample S3,the FNC/RGO/MDCF composite prepared by solvothermal method for 16 h,exhibited a minimum reflection loss(RL_(min))of-66.44 dB at a thickness of 2.29 mm.When the thickness was reduced to 1.50 mm,the optimal effective absorption bandwidth was 3.84 GHz.Analysis of the absorption mechanism of FNC/RGO/MDCF revealed that its excellent absorption performance was primarily attributed to the combined effects of conduction loss,multiple reflection,scattering,in-terface polarization,and dipole polarization.
基金supported by the Science and Technology Department of Qinghai Province,China(No.2022-ZJ-932Q).
文摘The increase in the utilization of infrared heat detection technology in military applications necessitates research on composites with improved thermal transmission performance and microwave absorption capabilities.This study satisfactorily fabricated a series of MoS_(2)/BN-xyz composites(which were characterized by the weight ratio of MoS_(2)to BN,denoted by xy:z)through chemical vapor depos-ition,which resulted in their improved thermal stability and thermal transmission performance.The results show that the remaining mass of MoS_(2)/BN-101 was as high as 69.25wt%at 800℃under air atmosphere,and a temperature difference of 31.7℃was maintained between the surface temperature and the heating source at a heating temperature of 200℃.Furthermore,MoS_(2)/BN-301 exhibited an im-pressive minimum reflection loss value of-32.21 dB at 4.0 mm and a wide effective attenuation bandwidth ranging from 9.32 to 18.00 GHz(8.68 GHz).Therefore,these simplified synthesized MoS_(2)/BN-xyz composites demonstrate great potential as highly efficient con-tenders for the enhancement of microwave absorption performance and thermal conductance.
基金financially supported by the National Natural Science Foundation of China(No.52231007)the Natural Science Foundation of Shaanxi Province(No.2022JM-248)+1 种基金the Creative Research Foundation of the Science and Technology on Thermostructural Composite Materials Laboratorythe Doctoral Scientific Research Foundation of Shaanxi University of Science&Technology(No.BJ16-06).
文摘The dielectric loss of carbon materials is closely related to the microstructure and the degree of crystallization,and the microstructure modulation of electromagnetic wave absorbing carbon materials is the key to enhancing absorption properties.In this work,a porous elastic Co@CNF-PDMS composite was prepared by freeze-drying and confined catalysis.The graphitization degree and conductivity loss of carbon nanofibers(CNFs)were regulated by heat treatment temperature and Co catalyst content.The construction of a heterointerface between Co and C enhances the interfacial polarization loss.The Co@CNF-PDMS composite with 4.5 mm achieves the minimum reflection loss(RLmin)of-81.0 dB at 9.9 GHz and RL no higher than-12.1 dB in the whole of the X-band.After applying a load of up to 40% strain and 100 cycles to Co@CNF-PDMS,the dielectric properties of the composite remain stable.With the increase of compression strain,the distribution density of the absorbent increases,and the CNF sheet layer extrusion contact forms a conductive path,which leads to the conductive loss increase,finally,the absorption band moves to a high frequency.The absorption band can be bi-directionally regulated by loading and strain with good stability,which provides a new strategy for the development of intelligent electromagnetic wave absorbing materials.
基金financially supported by the National Natural Science Foundation of China (52462032, 62274018, 52462031)Natural Science Foundation of Yunnan Province (202501AT070353, 202101BE070001-049)+2 种基金the Xinjiang Construction Corps Key Areas of Science and Technology Research Project (2023AB029)the Tianchi Talent Program of Xinjiang Uygur Autonomous Region (2024, Jiangzhao Chen)the Key Project of Chongqing Overseas Students Returning to China Entrepreneurship and Innovation Support Plan (cx2023006)。
文摘In recent years, the research advancements have high-lighted the critical role of the A-site cation in determining the optoelectronic and physicochemical properties of organicinorganic lead halide perovskites. Mixed-cation perovskites(MCPs) have been extensively used as absorber thin films in perovskite solar cells(PSCs), achieving high power conversion efficiencies(PCE) over 26%^([1, 2]).
基金National Natural Science Foundation of China (52371171, 52222106, 51971008, 52121001)Fund of National Key Laboratory of Scattering and Radiation (Beijing Institute of Environmental Features)。
文摘[Background and purposes]In recent years,there has been growing attention in academia and industry on the development of high-performance electromagnetic wave(EMW)absorbing materials.However,creating lightweight broadband absorbers remains a challenge in terms of practical applications.EMW absorbing materials primarily rely on the magnetic loss of magnetic materials and/or the dielectric loss of dielectric materials to convert EMW energy into thermal energy for dissipation.Among various magnetic materials,Fe_(3)O_(4) plays an irreplaceable role in EMW absorption due to its high saturation magnetization,low cost and compatible dielectric loss in the gigahertz frequency range.Nevertheless,the high density,large matching thickness and narrow absorption bandwidth of Fe_(3)O_(4) pose significant challenges for practical applications.In contrast,one-dimensional(1D)structures not only retain the characteristic properties of lightweight,chemical stability and high dielectric loss,but also exhibit anisotropic structures and large aspect ratios.Additionally,researchers have found that the minimum reflection loss(RL)of hollow carbon materials with mesopores is nearly four times that of non-porous hollow carbon materials and nine times that of dense carbon materials.According to Maxwell's EMW theory,composites consisting of Fe_(3)O_(4) and one-dimensional(1D)mesoporous carbon materials can leverage their respective advantages by optimizing the composition and structure of the composites to balance u,and Er,thereby enhancing EMW absorption performance.Additionally,numerous studies have demonstrated that composites composed of multi-component heterostructures significantly enhance the EAB.This enhancement is primarily ascribed to the numerous interface polarization losses generated by the additional heterostructure interfaces,which also improve the overall impedance matching of the composites.In this study,we leverage the advantages of magnetic/carbon composites,one-dimensional(1D)mesoporous carbon and multi-component heterostructures to prepare a composite of 1D mesoporous carbon-coated manganese oxide(Mn_(3)O_(4) and MnO,denoted as Mn_(x)O_(y))embedded with Fe_(3)0_(4) nanoparticles(Mn_(x)O_(y)/C@Fe_(3)O_(4)).This composite was synthesized and its formation mechanism and microstructure were analyzed in detail.At the same time,the influence of this Mn_(x)O_(y)/C@Fe_(3)O_(4) structure on EMW properties and absorbing performance was further discussed.[Methods]Firstly,MnO_(2) nanowires were synthesized by using a simple hydrothermal method.Then,the MnO_(2) nanowires served as templates for the synthesis of MnO_(2)/PDA@Fe^(3+)composites through the in-situ polymerization of dopamine and Fe^(3+)adsorption.Finally,1D mesoporous carbon-coated manganese oxide composite embedded with Fe_(3)O_(4) nanoparticles(Mn_(x)O_(y)/C@Fe_(3)O_(4))composites were obtained after heat treatment at 550℃ in N_(2).The crystal structure of the samples was analyzed using X-ray diffractometer with Cu Ka irradiation.Scanning electron microscopy(SEM)and high-resolution transmission electron microscopy(TEM)were used to observe microstructure and morphology of the samples.Nitrogen sorption measurements were obtained at 77 K on a Quantachrome surface area and pore size analyzer to measure the specific surface area and pore size distribution.XPS analysis was performed on X-ray photoelectron spectrometer with monochromatic Al Ka radiation.Magnetization curves of the samples were recorded with a Quantum Design physical property measurement system(PPMS-9)at room temperature.The electromagnetic parameters of the Mn_(x)O_(y)/C@Fe_(3)O_(4) composites were measured using an Agilent N5230C network analyzer in the frequency range of 2-18 GHz.For electromagentic testing,the Mn,Oy/C@Fe34 composites and paraffin wax were mixed at 50°C according to the mass ratio of 15 wt.%,20 wt.%and 25 wt.%,and pressed in a special mold to make coaxial rings(inner diameter=3.04 mm,outer diameter-7 mm),which were denoted as S-1,S-2 and S-3,respectively.[Results]SEM images illustrate the preparation process of iD mesoporous carbon-coated manganese oxide embedded with Fe3O4 nanoparticles composites(Mn_(x)O_(y)/C@Fe_(3)O_(4)).Most of the manganese oxide(Mn,Oy)was reduced to granular after heat treatment,while the outer carbon layer remains its 1D morphology and the carbon layer is interspersed with Fe_(3)O_(4) nanoparticles.The diffraction peaks of MnO_(2) nanowires align well with the body-centered tetragonal a-MnO2.For the Mn_(x)O_(y)/C@Fe_(3)O_(4) composites,the signals of α-MnO_(2) disappears,followed by the emergence of Mn_(3)O_(4) and three prominent diffraction peaks for the cubic MnO.In addition,four weak diffraction peaks correspond to the magnetite Fe_(3)O_(4),consistent with the HRTEM results.The corresponding nitrogen adsorption-desorption isotherm and pore size distribution curve are presented to further analyze the mesoporous structure of composite.The surface composition and element valence states of the Mn_(x)O_(y)/C@Fe_(3)O_(4) composite were investigated by using XPS.The polarization relaxation processes were analyzed according to the Debye theory which describes the relationship between e'and e".Besides the polarization loss,the contribution of the conduction loss plays an important role for the overall dielectric loss.The magnetization curve of Mn_(x)O_(y)/C@Fe_(3)O_(4) exhibits typical ferromagnetic behavior.The permittivity parameter(Co),defined as Co=u"(u)^(-2)f^(-1) determine the contribution of eddy current effect to magnetic loss.The tand values are all larger than those of tand,for the three samples,indicating that the loss capacity of Mn_(x)O_(y)/C@Fe_(3)O_(4) composites is mainly derived from the dielectric loss.Although tand,is smaller,it plays an important role in improving the impedance matching of Mn_(x)O_(y)/C@Fe_(3)O_(4) composites.When the filler loading is 15 wt.%,the RL of sample S-1 is about-10.0 dB at the thickness of 1.5 mm with narrow EAB.As the filler loading increased to 20 wt.%,the RL of sample S-2 reached-62.0 dB at a thickness of 2.2 mm and the EAB was 6.4 GHz at a small thickness of 1.7 mm.When the filler loading is further increased to 25 wt.%,the microwave absorption performance of sample S3 decreased significantly with a little region of RL<-10.0 dB at the thickness of 5.0 mm.The values of[Zin/Zol of the three samples at thicknesses of 1.5-5.0 mm were calculated.Due to good impedance matching of S-2,the incident EMW can enter the material and then can be dissipated through dipole polarization loss,interface polarization loss,conduction loss,eddy current loss and natural ferromagnetic resonance loss.[Conclusions]1D Mn_(x)O_(y)/C@Fe_(3)O_(4) was synthesized via a process involving the coating of polydopamine,adsorption of Fe(ll)salts and heat treatment,using MnO_(2) nanowires as templates.The multi-component heterostructure of the Mn_(x)O_(y)/C@Fe_(3)O_(4) composite(Mn_(3)O_(4),MnO,Fe_(3)O_(4),and C)enhances the interfacial interactions between the different phases,providing increased interface polarization loss under the action of an alternating electromagnetic field.The numerous defects and terminal groups in the mesoporous carbon provide abundant dipole polarization centers.Additionally,the presence of mesopores reduces the weight of the material while increasing the multiple scattering losses of the electromagnetic waves within the material.The ID carbon structure in the matrix forms a conductive network between adjacent fibers,facilitating electron migration and transition,thereby enhancing conductive loss.The incorporation of magnetic Fe_(3)O_(4) nanoparticles introduces eddy current loss and natural ferromagnetic resonance loss,thus increasing magnetic loss.Moreover,the synergistic effect between dielectric and magnetic losses improves the impedance matching of the material,leading to excellent EMW absorption performance.
基金Supported by Guangdong Basic and Applied Basic Research Fund,China(2024A1515012429)。
文摘As a representative transition metal dichalcogenides(TMD),NiTe_(2)has an ultra-fast optical response,high carrier mobility,and excellent environmental stability.It has a broad application prospect in the fields of ener-gy,biomedicine,optoelectronic devices,and so on.At present,there have been scant reports on the application of NiTe_(2)in the field of ultrafast photonics.In this work,NiTe_(2)was synthesized by chemical vapor deposition(CVD)and integrated with a tapered optical fiber to achieve mode-locking in an erbium-doped fiber laser(EDFL)and a thu-lium-doped fiber laser(TDFL).The mode-locked EDFL exhibited a pulse width of 678 fs and an output power of 3.92 mW.The pulse width of mode-locked TDFL was estimated to have a pulse width of 694 fs with an output power of 21.64 mW.These results demonstrate that NiTe_(2)is an effective saturable absorber material with potential applica-tions in the field of ultrafast optics.
文摘In this paper,a conventional soliton(CS)mode-locked erbium-doped fiber(EDF)laser was de-veloped using MAX phase material(MAX-PM)Nb_(4)AlC_(3)as a saturable absorber(SA).First,the liquid phase exfoliation(LPE)method was utilized to prepare Nb_(4)AlC_(3)nanosheets,and then a piece of tapered fiber was adopted to fabricate Nb_(4)AlC_(3)-SA.It was found that the saturation intensity and modulation depth of the Nb_(4)AlC_(3)-SA are 2.02 MW/cm^(2)and 1.88%.Based on the Nb_(4)AlC_(3)-SA,a conventional soliton(CS)mode-locked EDF laser was achieved.The central wavelength,pulse duration,and pulse repetition rate were found to be 1565.65 nm,615.37 fs,and 24.63 MHz,respectively.The performance is competitive and particularly superior in terms of pulse duration.This study fully confirms that Nb_(4)AlC_(3)possesses marvellous nonlinear saturable absorption properties and opens new possibilities for further research on air-stable ultrafast photon-ic devices.
文摘In today's era of continuous advancement in materials science,the properties of materials are constantly being enhanced,and their application fields are also expanding continuously.SAF(Super Absorbent Fiber),one such material,stands out.Compared to traditional SAP(Super Absorbent Polymer),SAF boasts a unique fibrous form and exceptional performance,presenting broad application prospects.
基金supported by the National Key R&D Program of China (Grant Nos. 2023YFC3010703, 2020YFB1708800, and 2023YFC3010705)。
文摘Optically transparent microwave absorbers and multi-band stealth have extensive potential applications in military defense and wireless communication fields, and thus have attracted considerable attention. So far,most related work is based on inorganic transparent conductive metasurfaces. In this paper, we proposed and experimentally demonstrated a flexible, broadband and optically transparent microwave absorber using an organic metasurface. The metasurface absorber is composed of a sandwich structure, in which electric resonances and magnetic resonances are induced resulting in broadband absorption. A spraying process was developed to prepare this metasurface absorber. Both simulations and experiment show that this metasurface has broadband microwave absorption and good optical transparency. We further found that by using a multi-layer structure, visible, radar,and infrared stealth(multi-band stealth) can be achieved simultaneously. With the advantages of excellent foldability and low cost, the proposed metasurfaces may have applications in military and wireless communication fields.
基金supported by the Natural Science Foundation of Guangdong Province (No.2023A1515010093)the Shenzhen Fundamental Research Program (Nos.JCYJ20220809170611004, JCYJ20231121110828001 and JCYJ20231121113641002)。
文摘Due to their unique physical properties,nonlinear materials are gradually demonstrating significant potential in the field of optics.Gold nanoparticles supported on carbon black(Au/CB),possessing low loss and high nonlinear characteristics,serve as an excellent material for saturable absorber(SA) in ultrafast fiber lasers.In this study,we investigated the performance of Au/CB material and designed an ultrafast fiber laser based on Au/CB SA,successfully observing stable fundamental mode-locking and pulse bunch phenomena.Specifically,when the fiber laser operates in fundamental mode-locking state,the center wavelength of optical spectrum is 1 558.82 nm,with a 3 dB bandwidth of 2.26 nm.Additionally,to investigate the evolution of real-time spectra,the dispersive Fourier transform(DFT) technology is employed.On the other hand,the pulse bunch emitted by the laser is actually composed of numerous random sub-pulses,exhibiting high-energy characteristics.The number of sub-pulses increases with the increase of pump power.These findings contribute to further exploring the properties of Au/CB material and reveal its potential applications in ultrafast optics.
基金the funding provided by the National Natural Science Foundation of China(Nos.62205038,62031006,62425106)the Natural Science Foundation of Chongqing Municipality of China(Nos.CSTB2023NSCQ-MSX0028,CSTB2022NSCQ-LZX0015)the Opening Subject of State Key Laboratory of Millimeter Waves of China(No.K202419)。
文摘Metasurfaces,which are two-dimensional arrays of subwavelength elements,enable versatile control of electromagnetic waves,thereby paving the way for advancements in electromagnetic stealth.Electromagnetic stealth aims to diminish object visibility to radar or other sensors by minimizing their reflection,scattering,or emission of electromagnetic waves.This paper reviews the latest works in microwave electromagnetic stealth devices utilizing metasurfaces,including absorbing,scattering,cloaking and multifunctional stealth techniques.A comprehensive analysis and characterization of these stealth metasurface based devices are presented,focusing on their working principles,performance characteristics,and the associated challenges.Additionally,we explore prospects and opportunities for further research.This paper offers a thorough and upto-date survey of the current status and future directions of this emerging field.
