We experimentally study the generation of a partially coherent non-diffractive beam by focusing a partially coherent vortex beam with an axieon. The investigation results show that when the partially coherent vortex b...We experimentally study the generation of a partially coherent non-diffractive beam by focusing a partially coherent vortex beam with an axieon. The investigation results show that when the partially coherent vortex beam is focused by the axicon, the beam is transferred into a partially coherent higher-order non-diffractive beam. In the non-diffractive zone, the transverse intensity distribution of the partially coherent higher-order non-diffractive beam is invariant during propagation. In addition, the range of the non-diffractive zone is related to the coherence of the partially coherent vortex beam. The poorer the coherence of the partially coherent vortex beam, the shorter the range of the non-diffractive zone.展开更多
The Bessel beam,characterized by its unique non-diffracting properties,holds promising applications.In this paper,we provide a detailed introduction and investigation into the theory and research of the Bessel beam,wi...The Bessel beam,characterized by its unique non-diffracting properties,holds promising applications.In this paper,we provide a detailed introduction and investigation into the theory and research of the Bessel beam,with a special focus on its generation and applications in the near-field region.We provide an introduction to the concepts,properties,and foundational theories of the Bessel beam.Additionally,the current study on generating Bessel beams and their applications is categorized and discussed,and potential research challenges are proposed in this paper.This review serves as a solid foundation for researchers to understand the concept of the Bessel beam and explore its potential applications.展开更多
Active control of surface plasmon polaritons(SPPs)is highly desired for nanophotonics.Here we employ a phase change material Ge_(2)Sb_(2)Te_(5)(GST)to actively manipulate the propagating direction of SPPs at the telec...Active control of surface plasmon polaritons(SPPs)is highly desired for nanophotonics.Here we employ a phase change material Ge_(2)Sb_(2)Te_(5)(GST)to actively manipulate the propagating direction of SPPs at the telecom wavelength.By utilizing the phase transition-induced refractive index change of GST,coupled with interference effects,a nanoantenna pair containing GST is designed to realize switchable one-way launching of SPPs.Devices based on the nanoantenna pairs are proposed to manipulate SPPs,including the direction tuning of SPP beams,switchable SPP focusing,and switchable cosine–Gauss SPP beam generating.Our design can be employed in compact optical circuits and photonics integration.展开更多
In this work,we introduce a kind of new structured radial grating,which is named the even-type sinusoidal amplitude radial(ETASR)grating.Based on diffraction theory and the principle of stationary phase,a comprehensiv...In this work,we introduce a kind of new structured radial grating,which is named the even-type sinusoidal amplitude radial(ETASR)grating.Based on diffraction theory and the principle of stationary phase,a comprehensive theoretical investigation on the diffraction patterns of ETASR gratings is conducted.Theoretical results show that novel carpet beams with beautiful optical structures and distinctive characteristics have been constructed on the basics of the ETASR grating.Their diffraction patterns are independent of propagation distance,that is,the new carpet beams have diffraction-free propagating characteristics.The non-diffracting carpet beams are divided into two types by beam characteristics:non-diffracting integer-order and half-integer-order carpet beams.Subsequently,we experimentally generate these carpet beams using the ETASR grating.Finally,their particularly interesting optical morphology and features are explored through numerical simulations and experiments.展开更多
Propagation-invariant beams have attracted major attention and presented applications in research areas such as particle acceleration,optical tweezers,and optical coherence tomography.On the basis of the introduced ra...Propagation-invariant beams have attracted major attention and presented applications in research areas such as particle acceleration,optical tweezers,and optical coherence tomography.On the basis of the introduced radial cosine phase gratings with high diffraction efficiency,this study observes a kind of novel shape-invariant radial lattice by assessing its Fresnel diffraction.Then,on the stationary phase principle,we originally construct and experimentally generate a family of new propagation-invariant[non-diffracting]radial lattices with polar symmetry.Their optical structures,propagation characteristics,and distinctive phase characteristics are studied.This study has important value for applying it in scientific fields in the future given that lattices have offered many applications,including optical communication in free space,quantum computation,quantum phase transition,spin–exchange interaction,and realization of magnetic fields.展开更多
Near-field technology is increasingly recognized due to its transformative potential in communication systems,establishing it as a critical enabler for sixth-generation(6G)telecommunication development.This paper pres...Near-field technology is increasingly recognized due to its transformative potential in communication systems,establishing it as a critical enabler for sixth-generation(6G)telecommunication development.This paper presents a comprehensive survey of recent advancements in near-field technology research.First,we explore the near-field propagation fundamentals by detailing definitions,transmission characteristics,and performance analysis.Next,we investigate various near-field channel models—deterministic,stochastic,and electromagnetic information theory based models,and review the latest progress in near-field channel testing,highlighting practical performance and limitations.With evolving channel models,traditional mechanisms such as channel estimation,beamtraining,and codebook design require redesign and optimization to align with near-field propagation characteristics.We then introduce innovative beam designs enabled by near-field technologies,focusing on non-diffractive beams(such as Bessel and Airy)and orbital angular momentum(OAM)beams,addressing both hardware architectures and signal processing frameworks,showcasing their revolutionary potential in near-field communication systems.Additionally,we highlight progress in both engineering and standardization,covering the primary 6G spectrum allocation,enabling technologies for near-field propagation,and network deployment strategies.Finally,we conclude by identifying promising future research directions for near-field technology development that could significantly impact system design.This comprehensive review provides a detailed understanding of the current state and potential of near-field technologies.展开更多
This paper proposes a new method to generate a two-dimensional(2D)Airy beam and Airy autofocusing beam by using the scalar holographic metasurface with amplitude-phase modulation in the microwave band.The proposed hol...This paper proposes a new method to generate a two-dimensional(2D)Airy beam and Airy autofocusing beam by using the scalar holographic metasurface with amplitude-phase modulation in the microwave band.The proposed holographic metasurface comprises subwavelength patch unit cells with a period of fewer than 1/8 wavelengths,which means that it has the finer sampling for electromagnetic waves and can simultaneously achieve precise modulations for the amplitude and phase of electromagnetic waves.Firstly,the 2D-Airy beam with quasi-non-diffraction and selfbending characteristics is generated,from which the holographic metasurface is designed to realize four different 2D-Airy beams with the same focus,achieving the 2D-Airy autofocusing beam in the microwave frequency.The holographic metasurface for Airy beam generation has high efficiency and an ultra-lower profile.Meanwhile,for applying the Airy beam in wireless power transfer(WPT),the efficiency of the generated Airy beam and Airy autofocusing beam is calculated for the first time in the microwave field.The simulation results show that the efficiency of the 2D-Airy beam can reach 66%at 150 mm away from the metasurface,while the efficiency of the 2D-Airy autofocusing beam at the focus,which is 280 mm from the metasurface,can reach 35%.The theoretical,simulated,and measured results show that the proposed method and holographic metasurfaces can flexibly achieve the special characteristics of self-autofocusing and self-bending Airy beams in the microwave domain,providing an effective path for wireless power transfer(WPT)scenario with radial obstructions.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No.60977068)the Foundations of the State Key Laboratory for Transient Optical and Photonic Technology of Chinese Academy of Sciences (Grant No.SKL ST200912)
文摘We experimentally study the generation of a partially coherent non-diffractive beam by focusing a partially coherent vortex beam with an axieon. The investigation results show that when the partially coherent vortex beam is focused by the axicon, the beam is transferred into a partially coherent higher-order non-diffractive beam. In the non-diffractive zone, the transverse intensity distribution of the partially coherent higher-order non-diffractive beam is invariant during propagation. In addition, the range of the non-diffractive zone is related to the coherence of the partially coherent vortex beam. The poorer the coherence of the partially coherent vortex beam, the shorter the range of the non-diffractive zone.
文摘The Bessel beam,characterized by its unique non-diffracting properties,holds promising applications.In this paper,we provide a detailed introduction and investigation into the theory and research of the Bessel beam,with a special focus on its generation and applications in the near-field region.We provide an introduction to the concepts,properties,and foundational theories of the Bessel beam.Additionally,the current study on generating Bessel beams and their applications is categorized and discussed,and potential research challenges are proposed in this paper.This review serves as a solid foundation for researchers to understand the concept of the Bessel beam and explore its potential applications.
文摘Active control of surface plasmon polaritons(SPPs)is highly desired for nanophotonics.Here we employ a phase change material Ge_(2)Sb_(2)Te_(5)(GST)to actively manipulate the propagating direction of SPPs at the telecom wavelength.By utilizing the phase transition-induced refractive index change of GST,coupled with interference effects,a nanoantenna pair containing GST is designed to realize switchable one-way launching of SPPs.Devices based on the nanoantenna pairs are proposed to manipulate SPPs,including the direction tuning of SPP beams,switchable SPP focusing,and switchable cosine–Gauss SPP beam generating.Our design can be employed in compact optical circuits and photonics integration.
基金supported by the National Natural Science Foundation of China(Nos.11974314 and 11674288).
文摘In this work,we introduce a kind of new structured radial grating,which is named the even-type sinusoidal amplitude radial(ETASR)grating.Based on diffraction theory and the principle of stationary phase,a comprehensive theoretical investigation on the diffraction patterns of ETASR gratings is conducted.Theoretical results show that novel carpet beams with beautiful optical structures and distinctive characteristics have been constructed on the basics of the ETASR grating.Their diffraction patterns are independent of propagation distance,that is,the new carpet beams have diffraction-free propagating characteristics.The non-diffracting carpet beams are divided into two types by beam characteristics:non-diffracting integer-order and half-integer-order carpet beams.Subsequently,we experimentally generate these carpet beams using the ETASR grating.Finally,their particularly interesting optical morphology and features are explored through numerical simulations and experiments.
基金supported by the National Natural Science Foundation of China(No.62475240)。
文摘Propagation-invariant beams have attracted major attention and presented applications in research areas such as particle acceleration,optical tweezers,and optical coherence tomography.On the basis of the introduced radial cosine phase gratings with high diffraction efficiency,this study observes a kind of novel shape-invariant radial lattice by assessing its Fresnel diffraction.Then,on the stationary phase principle,we originally construct and experimentally generate a family of new propagation-invariant[non-diffracting]radial lattices with polar symmetry.Their optical structures,propagation characteristics,and distinctive phase characteristics are studied.This study has important value for applying it in scientific fields in the future given that lattices have offered many applications,including optical communication in free space,quantum computation,quantum phase transition,spin–exchange interaction,and realization of magnetic fields.
基金Project supported by the Natural Science Foundation of Hunan Province,China(No.2022JJ40561)the Scientific Research Program of National University of Defense Technology,China(No.ZK22-46)the National Natural Science Foundation of China(Nos.61890542,62001481,and 62071475)。
文摘Near-field technology is increasingly recognized due to its transformative potential in communication systems,establishing it as a critical enabler for sixth-generation(6G)telecommunication development.This paper presents a comprehensive survey of recent advancements in near-field technology research.First,we explore the near-field propagation fundamentals by detailing definitions,transmission characteristics,and performance analysis.Next,we investigate various near-field channel models—deterministic,stochastic,and electromagnetic information theory based models,and review the latest progress in near-field channel testing,highlighting practical performance and limitations.With evolving channel models,traditional mechanisms such as channel estimation,beamtraining,and codebook design require redesign and optimization to align with near-field propagation characteristics.We then introduce innovative beam designs enabled by near-field technologies,focusing on non-diffractive beams(such as Bessel and Airy)and orbital angular momentum(OAM)beams,addressing both hardware architectures and signal processing frameworks,showcasing their revolutionary potential in near-field communication systems.Additionally,we highlight progress in both engineering and standardization,covering the primary 6G spectrum allocation,enabling technologies for near-field propagation,and network deployment strategies.Finally,we conclude by identifying promising future research directions for near-field technology development that could significantly impact system design.This comprehensive review provides a detailed understanding of the current state and potential of near-field technologies.
基金supported by National Natural Science Foundation of China(62288101 and 62001342)National Key Research and Development Program of China(2021YFA1401001)+1 种基金Key Research and Development Program of Shaanxi(2021TD-07)the Fundamental Research Funds for the Central Universities and the Innovation Fund of Xidian University。
文摘This paper proposes a new method to generate a two-dimensional(2D)Airy beam and Airy autofocusing beam by using the scalar holographic metasurface with amplitude-phase modulation in the microwave band.The proposed holographic metasurface comprises subwavelength patch unit cells with a period of fewer than 1/8 wavelengths,which means that it has the finer sampling for electromagnetic waves and can simultaneously achieve precise modulations for the amplitude and phase of electromagnetic waves.Firstly,the 2D-Airy beam with quasi-non-diffraction and selfbending characteristics is generated,from which the holographic metasurface is designed to realize four different 2D-Airy beams with the same focus,achieving the 2D-Airy autofocusing beam in the microwave frequency.The holographic metasurface for Airy beam generation has high efficiency and an ultra-lower profile.Meanwhile,for applying the Airy beam in wireless power transfer(WPT),the efficiency of the generated Airy beam and Airy autofocusing beam is calculated for the first time in the microwave field.The simulation results show that the efficiency of the 2D-Airy beam can reach 66%at 150 mm away from the metasurface,while the efficiency of the 2D-Airy autofocusing beam at the focus,which is 280 mm from the metasurface,can reach 35%.The theoretical,simulated,and measured results show that the proposed method and holographic metasurfaces can flexibly achieve the special characteristics of self-autofocusing and self-bending Airy beams in the microwave domain,providing an effective path for wireless power transfer(WPT)scenario with radial obstructions.
