Thirty years ago,Coullet et al.proposed that a special optical field exists in laser cavities bearing some analogy with the superfluid vortex.Since then,optical vortices have been widely studied,inspired by the hydrod...Thirty years ago,Coullet et al.proposed that a special optical field exists in laser cavities bearing some analogy with the superfluid vortex.Since then,optical vortices have been widely studied,inspired by the hydrodynamics sharing similar mathematics.Akin to a fluid vortex with a central flow singularity,an optical vortex beam has a phase singularity with a certain topological charge,giving rise to a hollow intensity distribution.Such a beam with helical phase fronts and orbital angular momentum reveals a subtle connection between macroscopic physical optics and microscopic quantum optics.These amazing properties provide a new understanding of a wide range of optical and physical phenomena,including twisting photons,spin–orbital interactions,Bose-Einstein condensates,etc.,while the associated technologies for manipulating optical vortices have become increasingly tunable and flexible.Hitherto,owing to these salient properties and optical manipulation technologies,tunable vortex beams have engendered tremendous advanced applications such as optical tweezers,high-order quantum entanglement,and nonlinear optics.This article reviews the recent progress in tunable vortex technologies along with their advanced applications.展开更多
Lightweight and high-efficiency microwave absorption materials with tunable electromagnetic properties is a highly sought-after goal and a great challenge for researchers. In this work, a simple strategy of confinedly...Lightweight and high-efficiency microwave absorption materials with tunable electromagnetic properties is a highly sought-after goal and a great challenge for researchers. In this work, a simple strategy of confinedly implanting small NiFe204 clusters on reduced graphene oxide is demonstrated, wherein the magnetic clusters are tailored, and more significantly, the electromagnetic properties are highly tuned. The microwave absorption was efficiently optimized yielding a maximum reflection loss of -58 dB and - 12 times broadening of the bandwidth （at -10 dB）. Furthermore, tailoring of the implanted magnetic clusters successfully realized the selective-frequency microwave absorption, and the absorption peak could shift from 4.6 to 16 GHz covering 72% of the measured frequency range. The fascinating performances eventuate from the appropriately tailored clusters, which provide optimal synergistic effects of the dielectric and magnetic loss caused by multi-relaxation, conductance, and resonances. These findings open new avenues for designing microwave absorption materials in future, and the well-tailored NiFe204-rGO can be readily applied as a multi-functional microwave absorption material in various fields ranging from civil and commerce to military and aerospace.展开更多
Metasurfaces,ultrathin metamaterials constructed by planar meta-atoms with tailored electromagnetic(EM)responses,have attracted tremendous attention due to their exotic abilities to freely control EM waves.With active...Metasurfaces,ultrathin metamaterials constructed by planar meta-atoms with tailored electromagnetic(EM)responses,have attracted tremendous attention due to their exotic abilities to freely control EM waves.With active elements incorporated into metasurface designs,one can realize tunable and/or reconfgurable metadevices with functionalities controlled by external stimuli,opening a new platform to dynamically manipulate EM waves.In this article,we briefy review recent progress on tunable/reconfgurable metasurfaces,focusing on their working mechanisms and practical applications.We frst describe available approaches,categorized into diferent classes based on external stimuli applied,to realize homogeneous tunable/reconfgurable metasurfaces,which can ofer uniform manipulations on EM waves.We next summarize recent achievements on inhomogeneous tunable/reconfgurable metasurfaces with constitutional meta-atoms locally tuned by external knobs,which can dynamically control the wave-fronts of EM waves.We conclude this review by presenting our own perspectives on possible future directions and existing challenges in this fast developing feld.展开更多
Fault diagnosis of rotating machinery is of great importance to the high quality products and long-term safe operation.However,the useful weak features are usually corrupted by strong background noise,thus increasing ...Fault diagnosis of rotating machinery is of great importance to the high quality products and long-term safe operation.However,the useful weak features are usually corrupted by strong background noise,thus increasing the difficulty of the feature extraction.Thereby,a novel denoising method based on the tunable Q-factor wavelet transform(TQWT)using neighboring coefficients is proposed in this article.The emerging TQWT possesses excellent properties compared with the conventional constant-Q wavelet transforms,which can tune Q-factor according to the oscillatory behavior of the signal.Meanwhile,neighboring coefficients denoising is adopted to avoid the overkill of conventional term-by-term thresholding techniques.Because of having the combined advantages of the two methods,the presented denoising method is more practical and effective than other methods.The proposed method is applied to a simulated signal,a rolling element bearing with an outer race defect from antenna transmission chain and a gearbox fault detection case.The processing results demonstrate that the proposed method can successfully identify the fault features,showing that this method is more effective than the conventional wavelet thresholding denoising methods,term-by-term TQWT denoising schemes and spectral kurtosis.展开更多
Holography,with the capability of recording and reconstructing wavefronts of light,has emerged as an ideal approach for future deep-immersive naked-eye display.However,the shortcomings(e.g.,small field of view,twin im...Holography,with the capability of recording and reconstructing wavefronts of light,has emerged as an ideal approach for future deep-immersive naked-eye display.However,the shortcomings(e.g.,small field of view,twin imaging,multiple or-ders of diffraction)of traditional dynamic holographic devices bring many challenges to their practical applications.Metasurfaces,planar artificial materials composed of subwavelength unit cells,have shown great potential in light field manipulation,which is useful for overcoming these drawbacks.Here,we review recent progress in the field of dynamic metasurface holography,from realization methods to design strategies,mainly including typical research works on dy-namic meta-holography based on tunable metasurfaces and multiplexed metasurfaces.Emerging applications of dynam-ic meta-holography have been found in 3D display,optical storage,optical encryption,and optical information pro-cessing,which may accelerate the development of light field manipulation and micro/nanofabrication with higher dimen-sions.A number of potential applications and possible development paths are also discussed at the end.展开更多
Metasurfaces, two-dimensional equivalents of metamaterials, are engineered surfaces consisting of deep subwavelength features that have full control of the electromagnetic waves. Metasurfaces are not only being applie...Metasurfaces, two-dimensional equivalents of metamaterials, are engineered surfaces consisting of deep subwavelength features that have full control of the electromagnetic waves. Metasurfaces are not only being applied to the current de-vices throughout the electromagnetic spectrum from microwave to optics but also inspiring many new thrilling applica-tions such as programmable on-demand optics and photonics in future. In order to overcome the limits imposed by pas-sive metasurfaces, extensive researches have been put on utilizing different materials and mechanisms to design active metasurfaces. In this paper, we review the recent progress in tunable and reconfigurable metasurfaces and metadevicesthrough the different active materials deployed together with the different control mechanisms including electrical, ther-mal, optical, mechanical, and magnetic, and provide the perspective for their future development for applications.展开更多
The 3D hollow hierarchi-cal architectures tend to be designed for inhibiting stack of MXene flakes to obtain satisfactory lightweight,high-e cient and broadband absorbers.Herein,the hollow NiCo compound@MXene networks...The 3D hollow hierarchi-cal architectures tend to be designed for inhibiting stack of MXene flakes to obtain satisfactory lightweight,high-e cient and broadband absorbers.Herein,the hollow NiCo compound@MXene networks were prepared by etching the ZIF 67 template and subsequently anchoring the Ti_(3)C_(2)Tx nanosheets through electrostatic self-assembly.The electromagnetic parameters and microwave absorption property can be distinctly or slightly regulated by adjusting the filler loading and decoration of Ti_(3)C_(2)Tx nanoflakes.Based on the synergistic e ectsof multi-components and special well-constructed structure,NiCo layered double hydroxides@Ti_(3)C_(2)Tx(LDHT-9)absorber remarkably achieves unexpected e ective absorption bandwidth(EAB)of 6.72 GHz with a thickness of 2.10 mm,covering the entire Ku-band.After calcination,transition metal oxide@Ti_(3)C_(2)Tx(TMOT-21)absorber near the percolation threshold possesses minimum reflection loss(RLmin)value of-67.22 dB at 1.70 mm within a filler loading of only 5 wt%.This work enlightens a simple strategy for constructing MXene-based composites to achieve high-e cient microwave absorbents with lightweight and tunable EAB.展开更多
Metasurfaces have attracted great attention due to their ability to manipulate the phase,amplitude,and polarization of light in a compact form.Tunable metasurfaces have been investigated recently through the integrati...Metasurfaces have attracted great attention due to their ability to manipulate the phase,amplitude,and polarization of light in a compact form.Tunable metasurfaces have been investigated recently through the integration with mechanically moving components and electrically tunable elements.Two interesting applications,in particular,are to vary the focal point of metalenses and to switch between holographic images.We present the recent progress on tunable metasurfaces focused on metalenses and metaholograms,including the basic working principles,advantages,and disadvantages of each working mechanism.We classify the tunable stimuli based on the light source and electrical bias,as well as others such as thermal and mechanical modulation.We conclude by summarizing the recent progress of metalenses and metaholograms,and providing our perspectives for the further development of tunable metasurfaces.展开更多
A series of fluorinated polyimide/POSS hybrid polymers（FPI-4-FPI-16） were prepared via a facile synthetic route using 2,2＇-bis（trifluoromethyl）benzidine, 4,4＇-oxydiphthalic dianhydride and monofunctional POSS as...A series of fluorinated polyimide/POSS hybrid polymers（FPI-4-FPI-16） were prepared via a facile synthetic route using 2,2＇-bis（trifluoromethyl）benzidine, 4,4＇-oxydiphthalic dianhydride and monofunctional POSS as starting materials. The hybrid polymers showed excellent solubility and film formation ability. Flexible and robust hybrid films could be conveniently obtained via solution-casting. The hybrid films demonstrated low dielectric constants and high thermal stability. Their dielectric constants were in the range of 2.47-2.92 at 1 MHz measured for their capacitance, and were tunable and decreased with an increase of POSS content. Their 10% weight loss temperatures were in the range of 539-591 ℃ and the weight residual at 800 ℃ ranged from 48% to 53% in nitrogen atmosphere. These hybrid films also possessed good mechanical properties and hydrophobic characteristics. This work could provide a potential strategy for the preparation of fluorinated polyimide/POSS hybrid polymers.展开更多
基金funded by The National Key Research and Development Program of China(Grant No.2017YFB1104500)Natural Science Foundation of Beijing Municipality(4172030)+3 种基金Beijing Young Talents Support Project(2017000020124G044)Leading talents of Guangdong province program(00201505)National Natural Science Foundation of China(U1701661,91750205,61975133,11604218,61975087)Natural Science Foundation of Guangdong Province(2016A030312010,2017A030313351).
文摘Thirty years ago,Coullet et al.proposed that a special optical field exists in laser cavities bearing some analogy with the superfluid vortex.Since then,optical vortices have been widely studied,inspired by the hydrodynamics sharing similar mathematics.Akin to a fluid vortex with a central flow singularity,an optical vortex beam has a phase singularity with a certain topological charge,giving rise to a hollow intensity distribution.Such a beam with helical phase fronts and orbital angular momentum reveals a subtle connection between macroscopic physical optics and microscopic quantum optics.These amazing properties provide a new understanding of a wide range of optical and physical phenomena,including twisting photons,spin–orbital interactions,Bose-Einstein condensates,etc.,while the associated technologies for manipulating optical vortices have become increasingly tunable and flexible.Hitherto,owing to these salient properties and optical manipulation technologies,tunable vortex beams have engendered tremendous advanced applications such as optical tweezers,high-order quantum entanglement,and nonlinear optics.This article reviews the recent progress in tunable vortex technologies along with their advanced applications.
基金This work was supported by the National Natural Science Foundation of China （NSFC） （Nos. 11774027, 51132002, 51072024 and 51372282）.
文摘Lightweight and high-efficiency microwave absorption materials with tunable electromagnetic properties is a highly sought-after goal and a great challenge for researchers. In this work, a simple strategy of confinedly implanting small NiFe204 clusters on reduced graphene oxide is demonstrated, wherein the magnetic clusters are tailored, and more significantly, the electromagnetic properties are highly tuned. The microwave absorption was efficiently optimized yielding a maximum reflection loss of -58 dB and - 12 times broadening of the bandwidth （at -10 dB）. Furthermore, tailoring of the implanted magnetic clusters successfully realized the selective-frequency microwave absorption, and the absorption peak could shift from 4.6 to 16 GHz covering 72% of the measured frequency range. The fascinating performances eventuate from the appropriately tailored clusters, which provide optimal synergistic effects of the dielectric and magnetic loss caused by multi-relaxation, conductance, and resonances. These findings open new avenues for designing microwave absorption materials in future, and the well-tailored NiFe204-rGO can be readily applied as a multi-functional microwave absorption material in various fields ranging from civil and commerce to military and aerospace.
基金This work was funded by the National Key Research and Development Program of China[Grant Nos.2017YFA0700201 and 2017YFA0303504]National Natural Science Foundation of China[Grant Nos.11734007,91850101,11674068,11874118,and 11474057]Natural Science Foundation of Shanghai[Grant Nos.16ZR1445200,16JC1403100,and 18ZR1403400].
文摘Metasurfaces,ultrathin metamaterials constructed by planar meta-atoms with tailored electromagnetic(EM)responses,have attracted tremendous attention due to their exotic abilities to freely control EM waves.With active elements incorporated into metasurface designs,one can realize tunable and/or reconfgurable metadevices with functionalities controlled by external stimuli,opening a new platform to dynamically manipulate EM waves.In this article,we briefy review recent progress on tunable/reconfgurable metasurfaces,focusing on their working mechanisms and practical applications.We frst describe available approaches,categorized into diferent classes based on external stimuli applied,to realize homogeneous tunable/reconfgurable metasurfaces,which can ofer uniform manipulations on EM waves.We next summarize recent achievements on inhomogeneous tunable/reconfgurable metasurfaces with constitutional meta-atoms locally tuned by external knobs,which can dynamically control the wave-fronts of EM waves.We conclude this review by presenting our own perspectives on possible future directions and existing challenges in this fast developing feld.
基金supported by the National Natural Science Foundation of China (Grant No. 51275384)the Key Project of National Natural Science Foundation of China (Grant No. 51035007)+1 种基金the Important National Science and Technology Specific Projects (Grant No. 2010ZX04014-016)the National Basic Research Program of China ("973" Program) (Grant No. 2009CB724405)
文摘Fault diagnosis of rotating machinery is of great importance to the high quality products and long-term safe operation.However,the useful weak features are usually corrupted by strong background noise,thus increasing the difficulty of the feature extraction.Thereby,a novel denoising method based on the tunable Q-factor wavelet transform(TQWT)using neighboring coefficients is proposed in this article.The emerging TQWT possesses excellent properties compared with the conventional constant-Q wavelet transforms,which can tune Q-factor according to the oscillatory behavior of the signal.Meanwhile,neighboring coefficients denoising is adopted to avoid the overkill of conventional term-by-term thresholding techniques.Because of having the combined advantages of the two methods,the presented denoising method is more practical and effective than other methods.The proposed method is applied to a simulated signal,a rolling element bearing with an outer race defect from antenna transmission chain and a gearbox fault detection case.The processing results demonstrate that the proposed method can successfully identify the fault features,showing that this method is more effective than the conventional wavelet thresholding denoising methods,term-by-term TQWT denoising schemes and spectral kurtosis.
基金financial supports from China Postdoctoral Science Foundation(2019M662597)Open Funding of State Key Laboratory of Optical Tech-nologies for Microfabrication(2019).
文摘Holography,with the capability of recording and reconstructing wavefronts of light,has emerged as an ideal approach for future deep-immersive naked-eye display.However,the shortcomings(e.g.,small field of view,twin imaging,multiple or-ders of diffraction)of traditional dynamic holographic devices bring many challenges to their practical applications.Metasurfaces,planar artificial materials composed of subwavelength unit cells,have shown great potential in light field manipulation,which is useful for overcoming these drawbacks.Here,we review recent progress in the field of dynamic metasurface holography,from realization methods to design strategies,mainly including typical research works on dy-namic meta-holography based on tunable metasurfaces and multiplexed metasurfaces.Emerging applications of dynam-ic meta-holography have been found in 3D display,optical storage,optical encryption,and optical information pro-cessing,which may accelerate the development of light field manipulation and micro/nanofabrication with higher dimen-sions.A number of potential applications and possible development paths are also discussed at the end.
文摘Metasurfaces, two-dimensional equivalents of metamaterials, are engineered surfaces consisting of deep subwavelength features that have full control of the electromagnetic waves. Metasurfaces are not only being applied to the current de-vices throughout the electromagnetic spectrum from microwave to optics but also inspiring many new thrilling applica-tions such as programmable on-demand optics and photonics in future. In order to overcome the limits imposed by pas-sive metasurfaces, extensive researches have been put on utilizing different materials and mechanisms to design active metasurfaces. In this paper, we review the recent progress in tunable and reconfigurable metasurfaces and metadevicesthrough the different active materials deployed together with the different control mechanisms including electrical, ther-mal, optical, mechanical, and magnetic, and provide the perspective for their future development for applications.
基金supported by the National Natural Science Foundation of China(No.52073010)Beijing Natural Science Foundation(2214069)。
文摘The 3D hollow hierarchi-cal architectures tend to be designed for inhibiting stack of MXene flakes to obtain satisfactory lightweight,high-e cient and broadband absorbers.Herein,the hollow NiCo compound@MXene networks were prepared by etching the ZIF 67 template and subsequently anchoring the Ti_(3)C_(2)Tx nanosheets through electrostatic self-assembly.The electromagnetic parameters and microwave absorption property can be distinctly or slightly regulated by adjusting the filler loading and decoration of Ti_(3)C_(2)Tx nanoflakes.Based on the synergistic e ectsof multi-components and special well-constructed structure,NiCo layered double hydroxides@Ti_(3)C_(2)Tx(LDHT-9)absorber remarkably achieves unexpected e ective absorption bandwidth(EAB)of 6.72 GHz with a thickness of 2.10 mm,covering the entire Ku-band.After calcination,transition metal oxide@Ti_(3)C_(2)Tx(TMOT-21)absorber near the percolation threshold possesses minimum reflection loss(RLmin)value of-67.22 dB at 1.70 mm within a filler loading of only 5 wt%.This work enlightens a simple strategy for constructing MXene-based composites to achieve high-e cient microwave absorbents with lightweight and tunable EAB.
基金financially supported by the POSCO-POSTECH-RIST Convergence Research Center program funded by POSCOthe National Research Foundation (NRF) grants (Grant Nos. NRF2019R1A2C3003129, CAMM-2019M3A6B3030637, and NRF-2019R1A5A8080290) funded by the Ministry of Science and ICT, Republic of Korea+1 种基金the Hyundai Motor Chung Mong-Koo fellowshipthe NRF fellowship (Grant No. NRF-2021R1A6A3A13038935) funded by the Ministry of Education, Republic of Korea
文摘Metasurfaces have attracted great attention due to their ability to manipulate the phase,amplitude,and polarization of light in a compact form.Tunable metasurfaces have been investigated recently through the integration with mechanically moving components and electrically tunable elements.Two interesting applications,in particular,are to vary the focal point of metalenses and to switch between holographic images.We present the recent progress on tunable metasurfaces focused on metalenses and metaholograms,including the basic working principles,advantages,and disadvantages of each working mechanism.We classify the tunable stimuli based on the light source and electrical bias,as well as others such as thermal and mechanical modulation.We conclude by summarizing the recent progress of metalenses and metaholograms,and providing our perspectives for the further development of tunable metasurfaces.
基金financially supported by the National Natural Science Foundation of China(No.21404016)Natural Science Foundation of Jiangsu Province(No.BK20141173)+1 种基金Opening Project of State Key Laboratory of Electrical Insulation and Power Equipment(No.EIPE14206)Qing Lan Project for Excellent Young Teachers of Jiangsu Province
文摘A series of fluorinated polyimide/POSS hybrid polymers（FPI-4-FPI-16） were prepared via a facile synthetic route using 2,2＇-bis（trifluoromethyl）benzidine, 4,4＇-oxydiphthalic dianhydride and monofunctional POSS as starting materials. The hybrid polymers showed excellent solubility and film formation ability. Flexible and robust hybrid films could be conveniently obtained via solution-casting. The hybrid films demonstrated low dielectric constants and high thermal stability. Their dielectric constants were in the range of 2.47-2.92 at 1 MHz measured for their capacitance, and were tunable and decreased with an increase of POSS content. Their 10% weight loss temperatures were in the range of 539-591 ℃ and the weight residual at 800 ℃ ranged from 48% to 53% in nitrogen atmosphere. These hybrid films also possessed good mechanical properties and hydrophobic characteristics. This work could provide a potential strategy for the preparation of fluorinated polyimide/POSS hybrid polymers.
