This paper introduces damping amplifier friction vibration absorbers(DAFVAs),compound damping amplifier friction vibration absorbers(CDAFVAs),nested damping amplifier friction vibration absorbers(NDAFVAs),and levered ...This paper introduces damping amplifier friction vibration absorbers(DAFVAs),compound damping amplifier friction vibration absorbers(CDAFVAs),nested damping amplifier friction vibration absorbers(NDAFVAs),and levered damping amplifier friction vibration absorbers(LDAFVAs)for controlling the structural vibrations and addressing the limitations of conventional tuned mass dampers(TMDs)and frictiontuned mass dampers(FTMDs).The closed-form analytical solution for the optimized design parameters is obtained using the H_(2)and H_(∞)optimization approaches.The efficiency of the recently established closed-form equations for the optimal design parameters is confirmed by the analytical examination.The closed form formulas for the dynamic responses of the main structure and the vibration absorbers are derived using the transfer matrix formulations.The foundation is provided by the harmonic and random-white noise excitations.Moreover,the effectiveness of the innovative dampers has been validated through numerical analysis.The optimal DAFVAs,CDAFVAs,NDAFVAs,and LDAFVAs exhibit at least 30%lower vibration reduction capacity compared with the optimal TMD.To demonstrate the effectiveness of the damping amplification mechanism,the novel absorbers are compared with a conventional FTMD.The results show that the optimized novel absorbers achieve at least 91%greater vibration reduction than the FTMD.These results show how the suggested designs might strengthen the structure's resilience to dynamic loads.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
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
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
In the field of broadband metamaterial absorbers,most research efforts have focused on optimizing the resonant layers and designing multi-layer structures,but relatively little attention has been paid to the dielectri...In the field of broadband metamaterial absorbers,most research efforts have focused on optimizing the resonant layers and designing multi-layer structures,but relatively little attention has been paid to the dielectric layers themselves.This paper proposed a method using carbonyl iron powder to modify the dielectric layer.This method significantly enhances the electromagnetic wave attenuation capability of the dielectric layer with the X-band range for metamaterial absorbers.A broadband absorber with a reflection loss(RL)of less than-10 dB within the frequency range of 4.98-18 GHz and covering the C,X,and Ku band was designed.This work analyzed the surface current distribution and the power loss distribution to elucidate the absorption mechanism of the absorber.It was found that the modified dielectric layer accounted for more than 30%of the total loss in the 2-18 GHz frequency band,and the effective absorption bandwidth(RL≤-10 dB)was almost twice that of the unmodified dielectric layer.This enhancement in absorption bandwidth is attributed to the introduction of a new electromagnetic wave loss mechanism by carbonyl iron powder.Meanwhile,the absorber exhibited good angular stability,maintaining at least 80%absorption(RL≤-7 dB)in the 7.0-18.0 GHz range even when the incident angle was increased to 60°.The experimental results showed that the measured results matched the simulation results well.Furthermore,compared with other methods for broadening the absorption bandwidth,the metamaterial absorber obtained by this method offers several advantages,including wideband absorption,thin profile,and a simple manufacturing process.This approach provides a new and promising direction for the design of broadband absorbers.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
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
Color plays an important role in the daily chemical product market,and transparent packaging of daily chemical products are loved by consumers,but it is difficult to avoid fading,discoloration or photodegradation of t...Color plays an important role in the daily chemical product market,and transparent packaging of daily chemical products are loved by consumers,but it is difficult to avoid fading,discoloration or photodegradation of the inner material of the product.UV light is a major contributor to colorant fading,which can affect color stability by damaging chromogenic groups and producing free radicals.In view of this,the combination of four ultraviolet absorbers DHHB,OS,OMC,and MCE was investigated,and the photostability of five common colorants in cosmetics was studied.After 28 days of photostability test,the pigment preservation rate was analyzed,and the results showed that 0.1%of the UV absorber compound could have a certain protective effect on the colorant,and 0.5%of the compound could significantly improve the photostability of the colorant.Adding ultraviolet absorbers to daily chemical products can significantly improve the fading,discoloration or photodegradation of colorants caused by ultraviolet rays.展开更多
Following publication of the original article[1],the authors found that they pasted the same data when drawing XRD for sample NCO-1 and NCO-2 in Fig.2a,however,the XRD of all four samples in the manuscript was tested,...Following publication of the original article[1],the authors found that they pasted the same data when drawing XRD for sample NCO-1 and NCO-2 in Fig.2a,however,the XRD of all four samples in the manuscript was tested,and XRD raw data were kept and can be offered.The correct Fig.2 has been provided in this Correction.展开更多
A lightweight composite resonator,consisting of a soft material acoustic black hole(SABH)and multiple vibration absorbers,is embedded in a plate to achieve localization and absorption of low-frequency vibration energy...A lightweight composite resonator,consisting of a soft material acoustic black hole(SABH)and multiple vibration absorbers,is embedded in a plate to achieve localization and absorption of low-frequency vibration energy.The combination of local and global admissible functions for displacement enhances the accuracy of the Ritz method in predicting vibration localization characteristics within the SABH domain.Utilizing soft materials for the SABH can reduce the mass and frequency of the composite resonator.Due to the lack of orthogonality between global vibration modes and localized modes,the low-frequency localized modes induced by the SABH are used to shape the initial global modes,thereby concentrating the global vibration of the plate in the SABH region.Consequently,the absorbers of the composite resonator only need to be a small fraction of the mass of the local SABH to achieve substantial vibration control of the host plate.This vibration localization strategy can significantly reduce the vibration amplitude of the host plate and enhance the effectiveness of lightweight absorbers in vibration reduction.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
In the last few years,research on advanced ultrafast photonic devices has attracted great interest from laser physicists.As a semiconductor material with excellent nonlinear saturation absorption characteristics,Ga As...In the last few years,research on advanced ultrafast photonic devices has attracted great interest from laser physicists.As a semiconductor material with excellent nonlinear saturation absorption characteristics,Ga As has been used in solidstate and fiber lasers as a mode-locker.However,the pulse widths that have been reported in the searchable published literature are all long and the shortest is tens of picoseconds.Femtosecond pulse widths,desired for a variety of applications,have not yet been reported in Ga As-based pulsed lasers.In this work,we further explore the nonlinear characteristics of Ga As that has been magnetron sputtered onto the surface of a tapered fiber and its application in the generation of femtosecond lasing via effective dispersion optimization and nonlinearity management.With the enhanced interaction between evanescent waves and Ga As nanosheets,mode-locked soliton pulses as short as 830 fs are generated at repetition rates of 4.64 MHz.As far as we know,this is the first time that femtosecond-level pulses have been generated with a Ga As-based saturable absorber.In addition,soliton molecules,including in the dual-pulse state,are also realized under stronger pumping.This work demonstrates that Ga As-based photonic devices have good application prospects in effective polymorphous ultrashort pulsed laser generation.展开更多
In order to meet the growing global energy demand and fulfill energy conservation and emission reduction goals, the efficient utilization of solar energy is becoming increasingly critical. However, the effects of high...In order to meet the growing global energy demand and fulfill energy conservation and emission reduction goals, the efficient utilization of solar energy is becoming increasingly critical. However, the effects of high temperatures on solar absorption are rarely considered in practical research. Therefore, this study presents a porous zinc and silver sulfide solar absorber with high-temperature radiative cooling capabilities. The solar absorption rate and radiative cooling efficiency in the high-temperature range(636 K–1060 K) are computed using the finite-difference time-domain method. Furthermore, the impact of parameters such as characteristic length, porosity, incident angle, and pore shape factor on both the absorption rate and efficiency of the solar absorber is analyzed. The mechanism is further examined from the perspective of microscopic thermal radiation. The results show that, in the high-temperature range, the solar absorption rate increases with higher porosity and incident angles, reaching its peak when the characteristic length is 1 μm. These findings highlight the significant potential of the solar absorber for efficient solar energy harvesting in photo-thermal conversion applications within a specific high-temperature range.展开更多
Transition metal disulfides are widely applied as nonlinear optical materials for laser pulse generation.In this paper,TaS_(2)is successfully used for the first time to achieve a high-energy passively Q-switched erbiu...Transition metal disulfides are widely applied as nonlinear optical materials for laser pulse generation.In this paper,TaS_(2)is successfully used for the first time to achieve a high-energy passively Q-switched erbium-doped fiber(EDF)laser.TaS_(2)nanosheets are prepared by the liquid phase exfoliation method,and then the TaS_(2)solution is mixed with polyvinyl alcohol(PVA).TaS_(2)/PVA film is prepared,which is cut into 1 mm×1 mm flakes.TaS_(2)/PVA saturable absorber(SA)is obtained by sandwiching a small flake between two fiber optic patch cable connectors.With the TaS_(2)/PVA SA added to an EDF laser,a Q-switched fiber laser with a center wavelength of 1560 nm and a repetition rate ranging from 51.33 k Hz to 83.04 k Hz is realized.At the pump power of 231 m W,the maximum output power is 1094μW,and the shortest pulse duration is 3.48μs.The results confirm that the TaS_(2)material has excellent potential for application in nonlinear optics.展开更多
Broadband and perfect terahertz absorber based on multilayer metamaterial using cross-ring patterned structures is proposed and investigated.The structure of the absorber is double absorption layers consisting of a ch...Broadband and perfect terahertz absorber based on multilayer metamaterial using cross-ring patterned structures is proposed and investigated.The structure of the absorber is double absorption layers consisting of a chromium cross ring and eight isosceles right triangles.The unique structure of the double absorbing layers excites the electric dipole multimode resonance,giving rise to high absorption performance.Meanwhile,the influence of construal parameters on absorber behavior is also discussed.The numerical results show that the absorption achieves over 90%ranging from 2.45 THz to 6.25 THz and 99%absorption in the range of 3.7—5.3 THz.The realization of broadband and perfect absorber is described using the impedance matching principle.It is obviously found that the absorber is insensitive to the high angle of incidence for both transverse electric(TE)and transverse magnetic(TM)polarizations.Compared with the former reports,this absorber has remarkable improved absorption efficiency and smaller period.The terahertz absorber may be found applications in the fields of energy capture and thermal detection.展开更多
Recently, Bi_(4)Br_(4) is proved to be a member of topological insulators and is expected to be a promising candidate for ultrafast photonic device. However, experimental studies on the nonlinear optical properties of...Recently, Bi_(4)Br_(4) is proved to be a member of topological insulators and is expected to be a promising candidate for ultrafast photonic device. However, experimental studies on the nonlinear optical properties of Bi_(4)Br_(4) are limited, and its broadband absorption capabilities have not been validated. This study presents the first preparation of Bi_(4)Br_(4) samples using the chemical vapor transport method, resulting in a saturable absorber(SA) with a high modulation depth(46.23%) and low non-saturable loss(6.5%). The optical nonlinearity ranks among the best in similar studies. Additionally, this work applies Bi_(4)Br_(4)-SA for the first time in 1-μm fiber laser, developing a ring-cavity mode-locked fiber laser with a central wavelength of 1029.79 nm, a pulse duration of 442 fs, and a maximum output power of 90.83 m W. And a linear-cavity mode-locked fiber laser with a central wavelength of 1031.24 nm, a pulse duration of 511 fs, and a maximum output power of 92.81 m W is constructed. It is worth noting that the optical-to-optical conversion efficiency has reached about 11.54% and 33.58%.This study verifies Bi_(4)Br_(4)-SA's modulation effectiveness for 1-μm pulse lasers and provides a powerful reference for the design of high-efficiency fiber lasers.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
In this paper,a tunable metamaterial absorber based on a Dirac semimetal is proposed.It consists of three different structures,from top to bottom,namely a double semicircular Dirac semimetal resonator,a silicon dioxid...In this paper,a tunable metamaterial absorber based on a Dirac semimetal is proposed.It consists of three different structures,from top to bottom,namely a double semicircular Dirac semimetal resonator,a silicon dioxide substrate and a continuous vanadium dioxide(VO_(2))reflector layer.When the Fermi energy level of the Dirac semimetal is 10 meV,the absorber absorbs more than 90%in the 39.06-84.76 THz range.Firstly,taking advantage of the tunability of the conductivity of the Dirac semimetal,dynamic tuning of the absorption frequency can be achieved by changing the Fermi energy level of the Dirac semimetal without the need to optimise the geometry and remanufacture the structure.Secondly,the structure has been improved by the addition of the phase change material VO_(2),resulting in a much higher absorption performance of the absorber.Since VO_(2)is a temperature-sensitive metal oxide with an insulating phase below the phase transition temperature(about 68℃)and a metallic phase above the phase transition temperature,this paper also analyses the effect of VO_(2)on the absorptive performance at different temperatures,with the aim of further improving absorber performance.展开更多
Metamaterials with artificial designability and perfect absorption provide a novel design method for the manipulation and attenuation of microwaves.However,owing to the limitations of meta-atomic reso-nance effect and...Metamaterials with artificial designability and perfect absorption provide a novel design method for the manipulation and attenuation of microwaves.However,owing to the limitations of meta-atomic reso-nance effect and the lossless medium,it is difficult to achieve effective microwave absorption in a broad-band frequency range.Hence,an ultra-wideband metamaterial absorber(UWMA)composed of two mag-netic media and a metasurface was designed,and the absorption bandwidth of 2.9 to 18 GHz for 90%absorptivity under normal incidence was achieved,covering almost the entire S,C,X,and Ku bands.Through detailed investigation of equivalent circuit,equivalent medium theory,electromagnetic field dis-tribution and front-back interface interference,the internal physical working mechanism was clarified essentially.In addition,the multi-environment adaptabilities of the proposed absorber,including polariza-tion sensitivity,large angle incidence,dual-station radar stealth,bearing capacity and corrosion resistance,were analyzed.The proposed metamaterial absorber presents an effective way to achieve ultra-wideband absorption and compatibility with environmental adaptability,and provides a new way of thinking for intelligent full-band stealth technology.展开更多
The article deals with the motion of the breech block carrier and the weapon casing of an automatic weapon mounted on a flexible carriage and the base of the weapon.Earlier works,which did not consider the dynamic pro...The article deals with the motion of the breech block carrier and the weapon casing of an automatic weapon mounted on a flexible carriage and the base of the weapon.Earlier works,which did not consider the dynamic properties of the base of the weapon,did not allow to reconcile the calculated and experimental results of the weapon casing displacement when shooting from firing rests.For the analysis of the motion of individual parts,the methods of mathematical modelling and firing experiments using a high-speed camera were chosen.Calculations show the best accord with experiment when modelling the system with 4 degrees of freedom.The oscillation of the system regarding the movement of the breech block carrier and the weapon casing was investigated under changed conditions of rate of fire,the use of a muzzle brake and different types of shock absorbers.The velocities and displacements of the weapon casing and the breech block carrier at different values of the impulse of the gases to the breech block carrier were determined.展开更多
基金the postdoctoral research grant received from the University of Glasgow for the partial financial support for this research work。
文摘This paper introduces damping amplifier friction vibration absorbers(DAFVAs),compound damping amplifier friction vibration absorbers(CDAFVAs),nested damping amplifier friction vibration absorbers(NDAFVAs),and levered damping amplifier friction vibration absorbers(LDAFVAs)for controlling the structural vibrations and addressing the limitations of conventional tuned mass dampers(TMDs)and frictiontuned mass dampers(FTMDs).The closed-form analytical solution for the optimized design parameters is obtained using the H_(2)and H_(∞)optimization approaches.The efficiency of the recently established closed-form equations for the optimal design parameters is confirmed by the analytical examination.The closed form formulas for the dynamic responses of the main structure and the vibration absorbers are derived using the transfer matrix formulations.The foundation is provided by the harmonic and random-white noise excitations.Moreover,the effectiveness of the innovative dampers has been validated through numerical analysis.The optimal DAFVAs,CDAFVAs,NDAFVAs,and LDAFVAs exhibit at least 30%lower vibration reduction capacity compared with the optimal TMD.To demonstrate the effectiveness of the damping amplification mechanism,the novel absorbers are compared with a conventional FTMD.The results show that the optimized novel absorbers achieve at least 91%greater vibration reduction than the FTMD.These results show how the suggested designs might strengthen the structure's resilience to dynamic loads.
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 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 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supported by the Key Research and Development Projects of Shaanxi Province,China(No.2020 ZDGY01-01)the Fundamental Research Funds for the Central Universities,China(No.D5000220202).
文摘In the field of broadband metamaterial absorbers,most research efforts have focused on optimizing the resonant layers and designing multi-layer structures,but relatively little attention has been paid to the dielectric layers themselves.This paper proposed a method using carbonyl iron powder to modify the dielectric layer.This method significantly enhances the electromagnetic wave attenuation capability of the dielectric layer with the X-band range for metamaterial absorbers.A broadband absorber with a reflection loss(RL)of less than-10 dB within the frequency range of 4.98-18 GHz and covering the C,X,and Ku band was designed.This work analyzed the surface current distribution and the power loss distribution to elucidate the absorption mechanism of the absorber.It was found that the modified dielectric layer accounted for more than 30%of the total loss in the 2-18 GHz frequency band,and the effective absorption bandwidth(RL≤-10 dB)was almost twice that of the unmodified dielectric layer.This enhancement in absorption bandwidth is attributed to the introduction of a new electromagnetic wave loss mechanism by carbonyl iron powder.Meanwhile,the absorber exhibited good angular stability,maintaining at least 80%absorption(RL≤-7 dB)in the 7.0-18.0 GHz range even when the incident angle was increased to 60°.The experimental results showed that the measured results matched the simulation results well.Furthermore,compared with other methods for broadening the absorption bandwidth,the metamaterial absorber obtained by this method offers several advantages,including wideband absorption,thin profile,and a simple manufacturing process.This approach provides a new and promising direction for the design of broadband absorbers.
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.
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Color plays an important role in the daily chemical product market,and transparent packaging of daily chemical products are loved by consumers,but it is difficult to avoid fading,discoloration or photodegradation of the inner material of the product.UV light is a major contributor to colorant fading,which can affect color stability by damaging chromogenic groups and producing free radicals.In view of this,the combination of four ultraviolet absorbers DHHB,OS,OMC,and MCE was investigated,and the photostability of five common colorants in cosmetics was studied.After 28 days of photostability test,the pigment preservation rate was analyzed,and the results showed that 0.1%of the UV absorber compound could have a certain protective effect on the colorant,and 0.5%of the compound could significantly improve the photostability of the colorant.Adding ultraviolet absorbers to daily chemical products can significantly improve the fading,discoloration or photodegradation of colorants caused by ultraviolet rays.
文摘Following publication of the original article[1],the authors found that they pasted the same data when drawing XRD for sample NCO-1 and NCO-2 in Fig.2a,however,the XRD of all four samples in the manuscript was tested,and XRD raw data were kept and can be offered.The correct Fig.2 has been provided in this Correction.
基金supported by the National Natural Science Foundation of China(Grant Nos.12302006,12132002,and 62188101).
文摘A lightweight composite resonator,consisting of a soft material acoustic black hole(SABH)and multiple vibration absorbers,is embedded in a plate to achieve localization and absorption of low-frequency vibration energy.The combination of local and global admissible functions for displacement enhances the accuracy of the Ritz method in predicting vibration localization characteristics within the SABH domain.Utilizing soft materials for the SABH can reduce the mass and frequency of the composite resonator.Due to the lack of orthogonality between global vibration modes and localized modes,the low-frequency localized modes induced by the SABH are used to shape the initial global modes,thereby concentrating the global vibration of the plate in the SABH region.Consequently,the absorbers of the composite resonator only need to be a small fraction of the mass of the local SABH to achieve substantial vibration control of the host plate.This vibration localization strategy can significantly reduce the vibration amplitude of the host plate and enhance the effectiveness of lightweight absorbers in vibration reduction.
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Project supported by the National Natural Science Foundation of China(Grant No.12164030)Young Science and Technology Talents of Inner Mongolia,China(Grant No.NJYT22101)+1 种基金the Central Government Guides Local Science,the Technology Development Fund Projects(Grant No.2023ZY0005)the Science and Technology Plan Projects of Inner Mongolia Autonomous Region of China(Grant No.2023KYPT0012)。
文摘In the last few years,research on advanced ultrafast photonic devices has attracted great interest from laser physicists.As a semiconductor material with excellent nonlinear saturation absorption characteristics,Ga As has been used in solidstate and fiber lasers as a mode-locker.However,the pulse widths that have been reported in the searchable published literature are all long and the shortest is tens of picoseconds.Femtosecond pulse widths,desired for a variety of applications,have not yet been reported in Ga As-based pulsed lasers.In this work,we further explore the nonlinear characteristics of Ga As that has been magnetron sputtered onto the surface of a tapered fiber and its application in the generation of femtosecond lasing via effective dispersion optimization and nonlinearity management.With the enhanced interaction between evanescent waves and Ga As nanosheets,mode-locked soliton pulses as short as 830 fs are generated at repetition rates of 4.64 MHz.As far as we know,this is the first time that femtosecond-level pulses have been generated with a Ga As-based saturable absorber.In addition,soliton molecules,including in the dual-pulse state,are also realized under stronger pumping.This work demonstrates that Ga As-based photonic devices have good application prospects in effective polymorphous ultrashort pulsed laser generation.
基金Project supported by the National Natural Science Foundation of China (Grant No. 52406102)Shandong Provincial Natural Science Foundation (Grant No. ZR2023QE258)。
文摘In order to meet the growing global energy demand and fulfill energy conservation and emission reduction goals, the efficient utilization of solar energy is becoming increasingly critical. However, the effects of high temperatures on solar absorption are rarely considered in practical research. Therefore, this study presents a porous zinc and silver sulfide solar absorber with high-temperature radiative cooling capabilities. The solar absorption rate and radiative cooling efficiency in the high-temperature range(636 K–1060 K) are computed using the finite-difference time-domain method. Furthermore, the impact of parameters such as characteristic length, porosity, incident angle, and pore shape factor on both the absorption rate and efficiency of the solar absorber is analyzed. The mechanism is further examined from the perspective of microscopic thermal radiation. The results show that, in the high-temperature range, the solar absorption rate increases with higher porosity and incident angles, reaching its peak when the characteristic length is 1 μm. These findings highlight the significant potential of the solar absorber for efficient solar energy harvesting in photo-thermal conversion applications within a specific high-temperature range.
基金Project supported by the National Natural Science Foundation of China(Grant No.12075190)the Shaanxi Fundamental Science Research Project for Mathematics and Physics(Grant No.23JSY019)。
文摘Transition metal disulfides are widely applied as nonlinear optical materials for laser pulse generation.In this paper,TaS_(2)is successfully used for the first time to achieve a high-energy passively Q-switched erbium-doped fiber(EDF)laser.TaS_(2)nanosheets are prepared by the liquid phase exfoliation method,and then the TaS_(2)solution is mixed with polyvinyl alcohol(PVA).TaS_(2)/PVA film is prepared,which is cut into 1 mm×1 mm flakes.TaS_(2)/PVA saturable absorber(SA)is obtained by sandwiching a small flake between two fiber optic patch cable connectors.With the TaS_(2)/PVA SA added to an EDF laser,a Q-switched fiber laser with a center wavelength of 1560 nm and a repetition rate ranging from 51.33 k Hz to 83.04 k Hz is realized.At the pump power of 231 m W,the maximum output power is 1094μW,and the shortest pulse duration is 3.48μs.The results confirm that the TaS_(2)material has excellent potential for application in nonlinear optics.
基金supported by the National Natural Science Foundation of China(No.61505160)the Innovation Capability Support Program of Shaanxi(No.2018KJXX-042)+1 种基金the Natural Science Basic Research Program of Shaanxi(No.2019JM-084)the State Key Laboratory of Transient Optics and Photonics(No.SKLST202108)。
文摘Broadband and perfect terahertz absorber based on multilayer metamaterial using cross-ring patterned structures is proposed and investigated.The structure of the absorber is double absorption layers consisting of a chromium cross ring and eight isosceles right triangles.The unique structure of the double absorbing layers excites the electric dipole multimode resonance,giving rise to high absorption performance.Meanwhile,the influence of construal parameters on absorber behavior is also discussed.The numerical results show that the absorption achieves over 90%ranging from 2.45 THz to 6.25 THz and 99%absorption in the range of 3.7—5.3 THz.The realization of broadband and perfect absorber is described using the impedance matching principle.It is obviously found that the absorber is insensitive to the high angle of incidence for both transverse electric(TE)and transverse magnetic(TM)polarizations.Compared with the former reports,this absorber has remarkable improved absorption efficiency and smaller period.The terahertz absorber may be found applications in the fields of energy capture and thermal detection.
基金Project supported by the Beijing Natural Science Foundation (Grant No. JQ21019)the National Key Research and Development Program of China (Grant Nos. 2022YFA1604200 and 2022YFA1204100)the Fund from Beijing Municipal Commission of Science and Technology (Grant No. Z231100006623006)。
文摘Recently, Bi_(4)Br_(4) is proved to be a member of topological insulators and is expected to be a promising candidate for ultrafast photonic device. However, experimental studies on the nonlinear optical properties of Bi_(4)Br_(4) are limited, and its broadband absorption capabilities have not been validated. This study presents the first preparation of Bi_(4)Br_(4) samples using the chemical vapor transport method, resulting in a saturable absorber(SA) with a high modulation depth(46.23%) and low non-saturable loss(6.5%). The optical nonlinearity ranks among the best in similar studies. Additionally, this work applies Bi_(4)Br_(4)-SA for the first time in 1-μm fiber laser, developing a ring-cavity mode-locked fiber laser with a central wavelength of 1029.79 nm, a pulse duration of 442 fs, and a maximum output power of 90.83 m W. And a linear-cavity mode-locked fiber laser with a central wavelength of 1031.24 nm, a pulse duration of 511 fs, and a maximum output power of 92.81 m W is constructed. It is worth noting that the optical-to-optical conversion efficiency has reached about 11.54% and 33.58%.This study verifies Bi_(4)Br_(4)-SA's modulation effectiveness for 1-μm pulse lasers and provides a powerful reference for the design of high-efficiency fiber lasers.
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.
文摘In this paper,a tunable metamaterial absorber based on a Dirac semimetal is proposed.It consists of three different structures,from top to bottom,namely a double semicircular Dirac semimetal resonator,a silicon dioxide substrate and a continuous vanadium dioxide(VO_(2))reflector layer.When the Fermi energy level of the Dirac semimetal is 10 meV,the absorber absorbs more than 90%in the 39.06-84.76 THz range.Firstly,taking advantage of the tunability of the conductivity of the Dirac semimetal,dynamic tuning of the absorption frequency can be achieved by changing the Fermi energy level of the Dirac semimetal without the need to optimise the geometry and remanufacture the structure.Secondly,the structure has been improved by the addition of the phase change material VO_(2),resulting in a much higher absorption performance of the absorber.Since VO_(2)is a temperature-sensitive metal oxide with an insulating phase below the phase transition temperature(about 68℃)and a metallic phase above the phase transition temperature,this paper also analyses the effect of VO_(2)on the absorptive performance at different temperatures,with the aim of further improving absorber performance.
基金National Natural Science Foundation of China(Nos.52103334,52071053,and U1704253)China Postdoctoral Science Foundation(Nos.2020M680946 and 2020M670748)+1 种基金Fundamental Research Funds for the Central Universities(No.DUT20GF111)Fundamental Research Funds of Shaanxi Key Laboratory of Artificially–Structured Functional Materials and Devices(No.AFMD–KFJJ–21102).
文摘Metamaterials with artificial designability and perfect absorption provide a novel design method for the manipulation and attenuation of microwaves.However,owing to the limitations of meta-atomic reso-nance effect and the lossless medium,it is difficult to achieve effective microwave absorption in a broad-band frequency range.Hence,an ultra-wideband metamaterial absorber(UWMA)composed of two mag-netic media and a metasurface was designed,and the absorption bandwidth of 2.9 to 18 GHz for 90%absorptivity under normal incidence was achieved,covering almost the entire S,C,X,and Ku bands.Through detailed investigation of equivalent circuit,equivalent medium theory,electromagnetic field dis-tribution and front-back interface interference,the internal physical working mechanism was clarified essentially.In addition,the multi-environment adaptabilities of the proposed absorber,including polariza-tion sensitivity,large angle incidence,dual-station radar stealth,bearing capacity and corrosion resistance,were analyzed.The proposed metamaterial absorber presents an effective way to achieve ultra-wideband absorption and compatibility with environmental adaptability,and provides a new way of thinking for intelligent full-band stealth technology.
基金supported by the Research project VAROPS(Military autonomous and robotic assets)of the Ministry of Defence of The Czech Republicby the Specific Research Support Project(Grant No.SV22-201)financed from funds of the Ministry of Education,Youth and Sports of The Czech Republic。
文摘The article deals with the motion of the breech block carrier and the weapon casing of an automatic weapon mounted on a flexible carriage and the base of the weapon.Earlier works,which did not consider the dynamic properties of the base of the weapon,did not allow to reconcile the calculated and experimental results of the weapon casing displacement when shooting from firing rests.For the analysis of the motion of individual parts,the methods of mathematical modelling and firing experiments using a high-speed camera were chosen.Calculations show the best accord with experiment when modelling the system with 4 degrees of freedom.The oscillation of the system regarding the movement of the breech block carrier and the weapon casing was investigated under changed conditions of rate of fire,the use of a muzzle brake and different types of shock absorbers.The velocities and displacements of the weapon casing and the breech block carrier at different values of the impulse of the gases to the breech block carrier were determined.
