The scattering of an electromagnetic high-order Bessel trigonometric beam by several typical homogeneous dielec- tric particles is investigated. The incident beam is represented by the vector expressions in Cartesian ...The scattering of an electromagnetic high-order Bessel trigonometric beam by several typical homogeneous dielec- tric particles is investigated. The incident beam is represented by the vector expressions in Cartesian coordinates. The scattering problems involving homogeneous dielectric particles are formulated with the surface integral equation method. As an example, the effects of the beam＇s parameters on the differential scattering cross section for a sphere are analyzed in detail. Then the numerical results for the scattering of a high-order Bessel trigonometric beam by three typical nonspherieal particles, including a spheroid, a cylinder, and a cube, are presented.展开更多
A comparison of differently polarized Bessel vortex beams propagating through a uniaxial anisotropic slab is discussed in terms of the vector wave function expansions.The magnitude profiles of electric field component...A comparison of differently polarized Bessel vortex beams propagating through a uniaxial anisotropic slab is discussed in terms of the vector wave function expansions.The magnitude profiles of electric field components, the transformation of polarization modes, and the distributions of orbital angular momentum(OAM) states of the reflected and transmitted beams for different incident angles are numerically simulated.The results indicate that the magnitude profiles of electric field components for different polarization modes are distinct from each other and have a great dependence on the incident angle,thus the transformation of polarization modes which reflects the change of energy can be affected largely.As compared to the x and circular polarization incidences, the reflected and transmitted beams for the radial polarization incidence suffer the fewest transformation of polarization modes, showing a better energy invariance.The distributions of OAM states of the reflected and transmitted beams for different polarization modes are diverse as well, and the derived OAM states of the transmitted beam for radial polarization present a focusing effect, concentrating on the state between two predominant OAM states.展开更多
The transmission of terahertz(THz)Bessel vortex beams through a multi-layered anisotropic magnetized plasma slab is investigated by using a hybrid method of cylindrical vector wave functions(CVWFs)and Fourier transfor...The transmission of terahertz(THz)Bessel vortex beams through a multi-layered anisotropic magnetized plasma slab is investigated by using a hybrid method of cylindrical vector wave functions(CVWFs)and Fourier transform.On the basis of the electromagnetic boundary conditions on each interface,a cascade form of expansion coefficients of the reflected and transmitted fields is obtained.Taking a double Gaussian distribution of the plasma density as an example,the influences of the applied magnetic field,the incident angle and polarization mode of the incident beams on the magnitude,OAM mode and polarization of the transmitted beams are analyzed in detail.The results indicate that the applied magnetic field has a major effect upon the polarization state of the transmitted fields but not upon the transmitted OAM spectrum.The incident angle has a powerful influence upon both the amplitude profile and the OAM spectrum of the transmitted beam.Furthermore,for multiple coaxial vortex beams,an increase of the maximum value of the plasma density causes more remarkable distortion of both the profile and OAM spectrum of the transmitted beam.This research makes a stable foundation for the THz OAM multiplexing/demultiplexing technology in a magnetized plasma environment.展开更多
In this Letter, we propose that the photopatterned liquid crystal(LC) can act as a broadband and efficient terahertz(THz) Bessel vortex beam(BVB) generator. The mechanism lies in the frequency-independent geometric ph...In this Letter, we propose that the photopatterned liquid crystal(LC) can act as a broadband and efficient terahertz(THz) Bessel vortex beam(BVB) generator. The mechanism lies in the frequency-independent geometric phase modulation induced by the spatially variant LC directors. By adopting large birefringence LCs and optimizing the cell gap, the maximized mode conversion efficiency can be continuously adjusted in broadband.Furthermore, the LC patterns can be designed and fabricated at will, which enables the THz BVBs to carry various topological charges. Such a THz LC BVB generator may facilitate the advanced THz imaging and communication apparatus.展开更多
We model the effects of weak fluctuations on the probability densities and normalized powers of vortex models for the Bessel–Gauss photon beam with fractional topological charge in the paraxial non-Kolmogorov turbule...We model the effects of weak fluctuations on the probability densities and normalized powers of vortex models for the Bessel–Gauss photon beam with fractional topological charge in the paraxial non-Kolmogorov turbulence channel. We find that probability density of signal vortex models is a function of deviation from the center of the photon beam, and the farther away from the beam center it is, the smaller the probability density is. For fractional topological charge, the average probability densities of signal/crosstalk vortex modes oscillate along the beam radius except the half-integer order. As the beam waist of the photon source grows, the average probability density of signal and crosstalk vortex modes grow together. Moreover, the peak of the average probability density of crosstalk vortex modes shifts outward from the beam center as the beam waist gets larger. The results also show that the smaller index of non-Kolmogorov turbulence and the smaller generalized refractive-index structure parameter may lead to the higher average probability densities of signal vortex modes and lower average probability densities of crosstalk vortex modes. Lower-coherence radius or beam waist can give rise to less reduction of the normalized powers of the signal vortex modes, which is opposite to the normalized powers of crosstalk vortex modes.展开更多
The applications of terahertz(THz)technology can be greatly extended using non-diffractive beams with unique field distributions and non-diffiactive transmission characteristics.Here,we design and experimentally demon...The applications of terahertz(THz)technology can be greatly extended using non-diffractive beams with unique field distributions and non-diffiactive transmission characteristics.Here,we design and experimentally demonstrate a set of dual non-diffractive THz beam generators based on an all-dielectric metasurface.Two kinds of non-diffractive beams with dramatically opposite focusing properties,Bessel beam and abruptly autofocus-ing(AAF)beam,are considered.A Bessel beam with longdistance non-diffractive characteristics and an AAF beam with low energy during transmission and abruptly increased energy near the focus are generated for x-and^-polarized incident waves,respectively.These two kinds of beams are characterized and the results agree well with simulations.In addition,we show numerically that these two kinds of beams can also carry orbital angular momentum by further imposing proper angular phases in the design.We believe that these metasurface-based beam generators have great potential use in THz imaging,communications,non-destructive evaluation,and many other fields.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 61308026 and 61431010the Fundamental Research Funds for the Central Universities of China under Grant No K5051307003
文摘The scattering of an electromagnetic high-order Bessel trigonometric beam by several typical homogeneous dielec- tric particles is investigated. The incident beam is represented by the vector expressions in Cartesian coordinates. The scattering problems involving homogeneous dielectric particles are formulated with the surface integral equation method. As an example, the effects of the beam＇s parameters on the differential scattering cross section for a sphere are analyzed in detail. Then the numerical results for the scattering of a high-order Bessel trigonometric beam by three typical nonspherieal particles, including a spheroid, a cylinder, and a cube, are presented.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61801349,61875156,and 61571355)the 111 Project,China(Grant No.B17035)
文摘A comparison of differently polarized Bessel vortex beams propagating through a uniaxial anisotropic slab is discussed in terms of the vector wave function expansions.The magnitude profiles of electric field components, the transformation of polarization modes, and the distributions of orbital angular momentum(OAM) states of the reflected and transmitted beams for different incident angles are numerically simulated.The results indicate that the magnitude profiles of electric field components for different polarization modes are distinct from each other and have a great dependence on the incident angle,thus the transformation of polarization modes which reflects the change of energy can be affected largely.As compared to the x and circular polarization incidences, the reflected and transmitted beams for the radial polarization incidence suffer the fewest transformation of polarization modes, showing a better energy invariance.The distributions of OAM states of the reflected and transmitted beams for different polarization modes are diverse as well, and the derived OAM states of the transmitted beam for radial polarization present a focusing effect, concentrating on the state between two predominant OAM states.
基金supported by National Natural Science Foundation of China(Nos.62171355,61801349,and 61875156)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2020JM-192)+1 种基金the Stable Support Project of Basic Scientific Research Institutes(Nos.A131901W14,A132001W12)the Science and Technology Foundation of State Key Laboratory of Electromagnetic Environment,and the 111 Project(No.B17035)。
文摘The transmission of terahertz(THz)Bessel vortex beams through a multi-layered anisotropic magnetized plasma slab is investigated by using a hybrid method of cylindrical vector wave functions(CVWFs)and Fourier transform.On the basis of the electromagnetic boundary conditions on each interface,a cascade form of expansion coefficients of the reflected and transmitted fields is obtained.Taking a double Gaussian distribution of the plasma density as an example,the influences of the applied magnetic field,the incident angle and polarization mode of the incident beams on the magnitude,OAM mode and polarization of the transmitted beams are analyzed in detail.The results indicate that the applied magnetic field has a major effect upon the polarization state of the transmitted fields but not upon the transmitted OAM spectrum.The incident angle has a powerful influence upon both the amplitude profile and the OAM spectrum of the transmitted beam.Furthermore,for multiple coaxial vortex beams,an increase of the maximum value of the plasma density causes more remarkable distortion of both the profile and OAM spectrum of the transmitted beam.This research makes a stable foundation for the THz OAM multiplexing/demultiplexing technology in a magnetized plasma environment.
基金supported by the National Natural Science Foundation of China (NSFC)(No. 61922038)the Fundamental Research Funds for the Central Universities (No. 14380170)。
文摘In this Letter, we propose that the photopatterned liquid crystal(LC) can act as a broadband and efficient terahertz(THz) Bessel vortex beam(BVB) generator. The mechanism lies in the frequency-independent geometric phase modulation induced by the spatially variant LC directors. By adopting large birefringence LCs and optimizing the cell gap, the maximized mode conversion efficiency can be continuously adjusted in broadband.Furthermore, the LC patterns can be designed and fabricated at will, which enables the THz BVBs to carry various topological charges. Such a THz LC BVB generator may facilitate the advanced THz imaging and communication apparatus.
基金supported by the Natural Science Foundation of Jiangsu Province of China(Grant No.BK20140128)the National Natural Science Foundation of Special Theoretical Physics(Grant No.11447174)the Fundamental Research Funds for the Central Universities(JUSRP51517)
文摘We model the effects of weak fluctuations on the probability densities and normalized powers of vortex models for the Bessel–Gauss photon beam with fractional topological charge in the paraxial non-Kolmogorov turbulence channel. We find that probability density of signal vortex models is a function of deviation from the center of the photon beam, and the farther away from the beam center it is, the smaller the probability density is. For fractional topological charge, the average probability densities of signal/crosstalk vortex modes oscillate along the beam radius except the half-integer order. As the beam waist of the photon source grows, the average probability density of signal and crosstalk vortex modes grow together. Moreover, the peak of the average probability density of crosstalk vortex modes shifts outward from the beam center as the beam waist gets larger. The results also show that the smaller index of non-Kolmogorov turbulence and the smaller generalized refractive-index structure parameter may lead to the higher average probability densities of signal vortex modes and lower average probability densities of crosstalk vortex modes. Lower-coherence radius or beam waist can give rise to less reduction of the normalized powers of the signal vortex modes, which is opposite to the normalized powers of crosstalk vortex modes.
基金the National Key Research and Development Program of China(No.2017YFA0701004)the National Natural Science Foundation of China(Grant Nos.61935015,61875150,61605143,61735012,61722509,and 61871212)+1 种基金Tianjin Municipal Fund for Distinguished Young Scholars(No.18JCJQJC45600)King Abdullah University of Science and Technology(KAUST)Office of Sponsored Research(OSR)(No.OSR-2016-CRG5-2950).
文摘The applications of terahertz(THz)technology can be greatly extended using non-diffractive beams with unique field distributions and non-diffiactive transmission characteristics.Here,we design and experimentally demonstrate a set of dual non-diffractive THz beam generators based on an all-dielectric metasurface.Two kinds of non-diffractive beams with dramatically opposite focusing properties,Bessel beam and abruptly autofocus-ing(AAF)beam,are considered.A Bessel beam with longdistance non-diffractive characteristics and an AAF beam with low energy during transmission and abruptly increased energy near the focus are generated for x-and^-polarized incident waves,respectively.These two kinds of beams are characterized and the results agree well with simulations.In addition,we show numerically that these two kinds of beams can also carry orbital angular momentum by further imposing proper angular phases in the design.We believe that these metasurface-based beam generators have great potential use in THz imaging,communications,non-destructive evaluation,and many other fields.
