The determination of optical force as a consequence of momentum transfer is inevitably subject to the use of the proper momentum density and stress tensor.It is imperative and valuable to consider the intrinsic scheme...The determination of optical force as a consequence of momentum transfer is inevitably subject to the use of the proper momentum density and stress tensor.It is imperative and valuable to consider the intrinsic scheme of photon momentum transfer,particularly when a particle is embedded in a complex dielectric environment.Typically,we consider a particle submerged in an inhomogeneous background composed of different dielectric materials,excluding coherent illumination or hydrodynamic effects.A ray-tracing method is adopted to capture the direct process of momentum transfer from the complex background medium,and this approach is validated using the modified Einstein–Laub method,which uses only the interior fields of the particle in the calculation.In this way,debates regarding the calculation of the force with different stress tensors using exterior fields can be avoided.Our suggested interpretation supports only the Minkowski approach for the optical momentum transfer to the embedded scatterer while rejecting Peierls’s and Abraham’s approaches,though the momentum of a stably moving photon in a continuous background medium should be considered to be of the Abraham type.Our interpretation also provides a novel method of realizing a tractor beam for the exertion of negative force that offers an alternative to the use of negative-index materials,optical gain,or highly non-paraxial or multiple-light interference.展开更多
For the traditional photonic crystal fibers with circular air holes, rectangular air holes are added to the fiber cladding. The periodic arrangement of the inner rectangular air holes allows the fiber structure to bet...For the traditional photonic crystal fibers with circular air holes, rectangular air holes are added to the fiber cladding. The periodic arrangement of the inner rectangular air holes allows the fiber structure to better match the annular mode field distribution of the vortex beam. The fiber structure was analyzed and calculated by COMSOL Multiphysics 5.4 finite element software, and the characteristics of fiber were analyzed, such as the dispersion, confinement loss, effective mode area and nonlinear coefficient. The results reveal that the photonic crystal fiber structure capable of carrying 50 orbital angular momentum (OAM) modes at the wavelength of 1.15 to 2.0 μm (850 nm). The effective refractive index difference Δneff between vector modes can reach 1 × 10-3, and larger difference can effectively separate the vector modes and improve the transmission performance of OAM modes. Moreover, the fiber has good performance, such as flat dispersion distribution of the low-order modes, low confinement loss below 10-9 dB·m-1, large effective mode field area and small nonlinear coefficient in the 850 nm wavelength range. Therefore, this fiber structure can be applied to the high-capacity communication system of fiber multiplexing OAM. In addition, the good characteristics of this fiber structure are of great significance for the transmission of vortex beam in fiber.展开更多
We calculate the canonical angular momentum of a free electron, positron and gamma photon. We show that for any particle with charge q the canonical angular momentum (J<sub>c</sub>) is written as the summa...We calculate the canonical angular momentum of a free electron, positron and gamma photon. We show that for any particle with charge q the canonical angular momentum (J<sub>c</sub>) is written as the summation of the kinetic angular momentum (J<sub>kin</sub>) and the intrinsic quantum flux dependent terms. In terms of the z-components this can be written as . For a free electron (e<sup>-</sup>) and a positron (e<sup>+</sup>) depending on the spin orientation we find that:;;and respectively. Similarly for a gamma (γ) photon, propagating in z direction with an angular frequency ω, the canonical angular momentum is found to be: , here the (+) and (-) signs stand for the right and left hand circular helicity respectively.展开更多
We investigate the neutron star magnetic field by the relative mean-field theory, where the photon effective mass depending on baryon density of charged particles is nonzero. This field is produced by star itself, whi...We investigate the neutron star magnetic field by the relative mean-field theory, where the photon effective mass depending on baryon density of charged particles is nonzero. This field is produced by star itself, which is the function of baryon density. The result fits the observations.展开更多
We have calculated the intrinsic magnetic moment of a photon through the intrinsic magnetic moment of a gamma photon created as a result of the electron-positron annihilation with the angular frequency ω. We show tha...We have calculated the intrinsic magnetic moment of a photon through the intrinsic magnetic moment of a gamma photon created as a result of the electron-positron annihilation with the angular frequency ω. We show that a photon propagating in z direction with an angular frequency ω carries a magnetic moment of μz = ±(ec/ω) along the propagation direction. Here, the (+) and (-) signs stand for the right hand and left circular helicity respectively. Because of these two symmetric values of the magnetic moment, we expect a splitting of the photon beam into two symmetric subbeams in a Stern-Gerlach experiment. The splitting is expected to be more prominent for low energy photons. We believe that the present result will be helpful for understanding the recent attempts on the Stern-Gerlach experiment with slow light and the behavior of the dark polaritons and also the atomic spinor polaritons.展开更多
There are two main theories about the origin of the Universe that show similitude with the Genesis writings, though in different verses: the Big Bang1 and the eternal Universe2 (an eventual quantum fluctuation). Howev...There are two main theories about the origin of the Universe that show similitude with the Genesis writings, though in different verses: the Big Bang1 and the eternal Universe2 (an eventual quantum fluctuation). However, it is possible to partially include the quantum theory in the Big Bang thanks to the nature of photons, to obtain a simple model. It is assumed as the origin of the Universe (space, time, matter and physical laws). A subsequent enormous expansion has been explained by a supposed brief Inflation period, followed up today by a constant adiabatic expansion acceleration. This paper assumes that the Universe is the total Space which contains the Physical Universe covered by an external, empty Space, both expanding at a constant Hubble acceleration ΓH [1]. A Big Bang design is intended by a deduction of the energy and number of primeval photons, from the present CMB value;they would have reacted whether to generate the Physical Universe or to decay till the CMB level. It follows an approach to the Universe expansion work, based on the Hubble field (VH) as well as on Thermo-dynamics. They are calculated: the time and angular momentum required for the Physical Universe to reach the maximum internal velocity c as well as, simultaneously, a c tangential velocity. The Universe luminosity at different periods and the adequate expressions of parameters (Ω, q, k) are revised. It is proposed a modification in the equation of the H(t) parameter and the Ho value. The operator of convective derivative is applied to obtain an equation of continuity for the photonic energy;an adiabatic Jacobian gives similar results. This essay differs from others based on black box radiation, since the Universe has no walls and the photons energy decays continuously.展开更多
Using the coherent state representation of Wigner operator and the technique of integration within an ordered product （IWOP） of operators, this paper derives the Wigner functions for the photon-depleted even and odd...Using the coherent state representation of Wigner operator and the technique of integration within an ordered product （IWOP） of operators, this paper derives the Wigner functions for the photon-depleted even and odd coherent states （PDEOCSs）. Moreover, in terms of the Wigner functions with respect to the complex parameter a the nonclassical properties of the PDEOCSs are discussed. The results show that the nonclassicality for the state ｜β, m〉o （or ｜β,m〉e） is more pronounced when m is even （or odd）. According to the marginal distributions of the Wigner functions, the physical meaning of the Wigner functions is given. Further, the tomograms of the PDEOCSs are calculated with the aid of newly introduced intermediate coordinate-momentum representation in quantum optics.展开更多
Spatiotemporal optical vortex(STOV)pulses can carry transverse orbital angular momentum(OAM)that is perpendicular to the direction of pulse propagation.For a STOV pulse,its spatiotemporal profile can be significantly ...Spatiotemporal optical vortex(STOV)pulses can carry transverse orbital angular momentum(OAM)that is perpendicular to the direction of pulse propagation.For a STOV pulse,its spatiotemporal profile can be significantly distorted due to unbalanced dispersive and diffractive phases.This may limit its use in many research applications,where a long interaction length and a tight confinement of the pulse are needed.The first demonstration of STOV pulse propagation through a few-mode optical fiber is presented.Both numerical and experimental analysis on the propagation of STOV pulse through a commercially available SMF-28 standard telecommunication fiber is performed.The spatiotemporal phase feature of the pulse can be well kept after the pulse propagates a few-meter length through the fiber even with bending.Further propagation of the pulse will result in a breakup of its spatiotemporal spiral phase structure due to an excessive amount of modal group delay dispersion.The stable and robust transmission of transverse photonic OAM through optical fiber may open new opportunities for transverse photonic OAM studies in telecommunications,OAM lasers,and nonlinear fiber-optical research.展开更多
基金CWQ acknowledges financial support from the National University of Singapore(Grant No.R-263-000-678-133)ZW acknowledges support from the Packard Fellowship in Science and Engineering and the Alfred P.Sloan Research Fellowship.CWQ and WD contributed equally。
文摘The determination of optical force as a consequence of momentum transfer is inevitably subject to the use of the proper momentum density and stress tensor.It is imperative and valuable to consider the intrinsic scheme of photon momentum transfer,particularly when a particle is embedded in a complex dielectric environment.Typically,we consider a particle submerged in an inhomogeneous background composed of different dielectric materials,excluding coherent illumination or hydrodynamic effects.A ray-tracing method is adopted to capture the direct process of momentum transfer from the complex background medium,and this approach is validated using the modified Einstein–Laub method,which uses only the interior fields of the particle in the calculation.In this way,debates regarding the calculation of the force with different stress tensors using exterior fields can be avoided.Our suggested interpretation supports only the Minkowski approach for the optical momentum transfer to the embedded scatterer while rejecting Peierls’s and Abraham’s approaches,though the momentum of a stably moving photon in a continuous background medium should be considered to be of the Abraham type.Our interpretation also provides a novel method of realizing a tractor beam for the exertion of negative force that offers an alternative to the use of negative-index materials,optical gain,or highly non-paraxial or multiple-light interference.
文摘For the traditional photonic crystal fibers with circular air holes, rectangular air holes are added to the fiber cladding. The periodic arrangement of the inner rectangular air holes allows the fiber structure to better match the annular mode field distribution of the vortex beam. The fiber structure was analyzed and calculated by COMSOL Multiphysics 5.4 finite element software, and the characteristics of fiber were analyzed, such as the dispersion, confinement loss, effective mode area and nonlinear coefficient. The results reveal that the photonic crystal fiber structure capable of carrying 50 orbital angular momentum (OAM) modes at the wavelength of 1.15 to 2.0 μm (850 nm). The effective refractive index difference Δneff between vector modes can reach 1 × 10-3, and larger difference can effectively separate the vector modes and improve the transmission performance of OAM modes. Moreover, the fiber has good performance, such as flat dispersion distribution of the low-order modes, low confinement loss below 10-9 dB·m-1, large effective mode field area and small nonlinear coefficient in the 850 nm wavelength range. Therefore, this fiber structure can be applied to the high-capacity communication system of fiber multiplexing OAM. In addition, the good characteristics of this fiber structure are of great significance for the transmission of vortex beam in fiber.
文摘We calculate the canonical angular momentum of a free electron, positron and gamma photon. We show that for any particle with charge q the canonical angular momentum (J<sub>c</sub>) is written as the summation of the kinetic angular momentum (J<sub>kin</sub>) and the intrinsic quantum flux dependent terms. In terms of the z-components this can be written as . For a free electron (e<sup>-</sup>) and a positron (e<sup>+</sup>) depending on the spin orientation we find that:;;and respectively. Similarly for a gamma (γ) photon, propagating in z direction with an angular frequency ω, the canonical angular momentum is found to be: , here the (+) and (-) signs stand for the right and left hand circular helicity respectively.
基金the Key Research Plan of Theoretical Physics and Cross Science
文摘We investigate the neutron star magnetic field by the relative mean-field theory, where the photon effective mass depending on baryon density of charged particles is nonzero. This field is produced by star itself, which is the function of baryon density. The result fits the observations.
文摘We have calculated the intrinsic magnetic moment of a photon through the intrinsic magnetic moment of a gamma photon created as a result of the electron-positron annihilation with the angular frequency ω. We show that a photon propagating in z direction with an angular frequency ω carries a magnetic moment of μz = ±(ec/ω) along the propagation direction. Here, the (+) and (-) signs stand for the right hand and left circular helicity respectively. Because of these two symmetric values of the magnetic moment, we expect a splitting of the photon beam into two symmetric subbeams in a Stern-Gerlach experiment. The splitting is expected to be more prominent for low energy photons. We believe that the present result will be helpful for understanding the recent attempts on the Stern-Gerlach experiment with slow light and the behavior of the dark polaritons and also the atomic spinor polaritons.
文摘There are two main theories about the origin of the Universe that show similitude with the Genesis writings, though in different verses: the Big Bang1 and the eternal Universe2 (an eventual quantum fluctuation). However, it is possible to partially include the quantum theory in the Big Bang thanks to the nature of photons, to obtain a simple model. It is assumed as the origin of the Universe (space, time, matter and physical laws). A subsequent enormous expansion has been explained by a supposed brief Inflation period, followed up today by a constant adiabatic expansion acceleration. This paper assumes that the Universe is the total Space which contains the Physical Universe covered by an external, empty Space, both expanding at a constant Hubble acceleration ΓH [1]. A Big Bang design is intended by a deduction of the energy and number of primeval photons, from the present CMB value;they would have reacted whether to generate the Physical Universe or to decay till the CMB level. It follows an approach to the Universe expansion work, based on the Hubble field (VH) as well as on Thermo-dynamics. They are calculated: the time and angular momentum required for the Physical Universe to reach the maximum internal velocity c as well as, simultaneously, a c tangential velocity. The Universe luminosity at different periods and the adequate expressions of parameters (Ω, q, k) are revised. It is proposed a modification in the equation of the H(t) parameter and the Ho value. The operator of convective derivative is applied to obtain an equation of continuity for the photonic energy;an adiabatic Jacobian gives similar results. This essay differs from others based on black box radiation, since the Universe has no walls and the photons energy decays continuously.
基金Project supported by the National Natural Science Foundation of China (Grant No 10574060)the Natural Science Foundation of Shandong Province of China (Grant No Y2004A09)
文摘Using the coherent state representation of Wigner operator and the technique of integration within an ordered product （IWOP） of operators, this paper derives the Wigner functions for the photon-depleted even and odd coherent states （PDEOCSs）. Moreover, in terms of the Wigner functions with respect to the complex parameter a the nonclassical properties of the PDEOCSs are discussed. The results show that the nonclassicality for the state ｜β, m〉o （or ｜β,m〉e） is more pronounced when m is even （or odd）. According to the marginal distributions of the Wigner functions, the physical meaning of the Wigner functions is given. Further, the tomograms of the PDEOCSs are calculated with the aid of newly introduced intermediate coordinate-momentum representation in quantum optics.
基金We acknowledge support from the National Natural Science Foundation of China(NSFC)[Grant Nos.92050202(Q.Z.)and 12104309(Q.C.)]the Shanghai Science and Technology Committee[Grant No.19060502500(Q.Z.)],the Shanghai Sailing Program[Grant No.21YF1431500(Q.C.)]the National Research Foundation of Korea(NRF)funded by the Korea government(MSIT)[Grant No.2022R1A2C1091890(A.C.)].
文摘Spatiotemporal optical vortex(STOV)pulses can carry transverse orbital angular momentum(OAM)that is perpendicular to the direction of pulse propagation.For a STOV pulse,its spatiotemporal profile can be significantly distorted due to unbalanced dispersive and diffractive phases.This may limit its use in many research applications,where a long interaction length and a tight confinement of the pulse are needed.The first demonstration of STOV pulse propagation through a few-mode optical fiber is presented.Both numerical and experimental analysis on the propagation of STOV pulse through a commercially available SMF-28 standard telecommunication fiber is performed.The spatiotemporal phase feature of the pulse can be well kept after the pulse propagates a few-meter length through the fiber even with bending.Further propagation of the pulse will result in a breakup of its spatiotemporal spiral phase structure due to an excessive amount of modal group delay dispersion.The stable and robust transmission of transverse photonic OAM through optical fiber may open new opportunities for transverse photonic OAM studies in telecommunications,OAM lasers,and nonlinear fiber-optical research.
