Author

# Hua-Feng Xu

Other affiliations: Chinese Academy of Sciences, Anhui Normal University, University of Science and Technology of China

Bio: Hua-Feng Xu is an academic researcher from Anhui University of Science and Technology. The author has contributed to research in topics: Beam (structure) & Coherence length. The author has an hindex of 8, co-authored 21 publications receiving 153 citations. Previous affiliations of Hua-Feng Xu include Chinese Academy of Sciences & Anhui Normal University.

##### Papers

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TL;DR: It has been found that the CGSM beam has advantage over the Gaussian Schell-model (GSM) beam for reducing the turbulence-induced degradation, and this advantage will be more obvious for the beams with larger parameter n and spatial coherence δ or under the condition of stronger fluctuation of turbulence.

Abstract: Based on the extended Huygens-Fresnel principle and second-order moments of the Wigner distribution function (WDF), we have studied the relative root-mean-square (rms) angular width and the propagation factor of cosine-Gaussian-correlated Schell-model (CGSM) beams propagating in non-Kolmogorov turbulence. It has been found that the CGSM beam has advantage over the Gaussian Schell-model (GSM) beam for reducing the turbulence-induced degradation, and this advantage will be more obvious for the beams with larger parameter n and spatial coherence δ or under the condition of stronger fluctuation of turbulence. The CGSM beam with larger parameter n or smaller spatial coherence δ will be less affected by the turbulence. In addition, the effects of the slope-parameter α, inner and outer scale and the refractive-index structure constant of the non-Kolmogorov’s power spectrum on the propagation factor are also analyzed in detailed.

31 citations

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TL;DR: The numerical results show that the probability of the signal OAM state remains almost invariant when the radius of the receiver aperture varies, thus it can be optimized by choosing a suitable value of the Radius of the Receiver aperture.

Abstract: We derive the probabilities of the signal OAM state and crosstalk OAM state for a Laguerre-Gaussian (LG) beam propagating through Kolmogorov and Non-Kolmogorov turbulence, and derive the accurate analytical function of the probability for the received OAM state modulated by an arbitrary receiver aperture. The probability of the detected OAM state with a receiver aperture for different values of the radius is demonstrated numerically. Our numerical results show that the probability of the signal OAM state remains almost invariant when the radius of the receiver aperture varies. The probability of the crosstalk OAM state decreases with the decrease of the radius of the receiver aperture, thus it can be optimized by choosing a suitable value of the radius of the receiver aperture. Our results will be useful in free-space optical communications.

30 citations

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TL;DR: Numerical results show that the focal intensity distributions of the radially polarized MGSM vortex beam can be shaped by regulating the structure of the correlation functions and the topological charge of vortex phase, and some focal fields with novel structure can be formed by choosing suitable fractional values of topological charges and spatial coherence length.

Abstract: In this paper, we have introduced a new class of partially coherent vector vortex beams, named radially polarized multi-Gaussian Schell-model (MGSM) vortex beam, carrying the vortex phase with tunable topological charges (i.e., both integral and fractional values) as a natural extension of the radially polarized MGSM beam. The tight focusing properties of the radially polarized MGSM vortex beam passing through a high numerical aperture (NA) objective lens are investigated numerically based on the vectorial diffraction theory. Numerical results show that the focal intensity distributions of the radially polarized MGSM vortex beam can be shaped by regulating the structure of the correlation functions and the topological charge of vortex phase. In contrast with the integral vortex beam, the most intriguing property of the fractional vortex beam is that the focal intensity distribution at the focal plane can be nonuniformity and asymmetry, while such unique characteristics will vanish when the spatial coherence length is sufficiently small. Furthermore, some focal fields with novel structure, such as a focal spot with nonuniform asymmetric or an anomalous asymmetric hollow focal field, can be formed by choosing suitable fractional values of topological charge and spatial coherence length. Our results will be useful for optical trapping, especially for trapping of irregular particles or manipulation of absorbing particles.

28 citations

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TL;DR: A new kind of partially coherent vector beam with special correlation function and vortex phase named radially polarized Laguerre-Gaussian-correlated Schell-model (LGCSM) vortex beam is introduced as a natural extension of scalar LGCSM vortex beam and the realizability conditions for such beam are derived.

Abstract: In this paper, we introduce a new kind of partially coherent vector beam with special correlation function and vortex phase named radially polarized Laguerre-Gaussian-correlated Schell-model (LGCSM) vortex beam as a natural extension of scalar LGCSM vortex beam The realizability conditions for such beam are derived The tight focusing properties of a radially polarized LGCSM vortex beam passing through a high numerical aperture (NA) objective lens are investigated numerically based on the vectorial diffraction theory We find that not only the transverse component but also the longitudinal component of the focal field distributions can be shaped by regulating the structures of the correlation functions, which is quite different from that of the conventional radially polarized partially coherent beam Moreover, a series of wildly used focal field with novel structure, eg, focal spot, flat-topped or doughnut beam profiles, needle-like focal field and controllable three-dimensional (3D) optical cage, were obtained These results indicate that the focus shaping can be achieved by combining the regulation of the structures of the correlation functions with the regulation of beam parameters effectively Our results may be useful for potential applications in optical trapping, optical high-resolution microscopy and optical data storage

22 citations

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TL;DR: Based on the Rayleigh scattering theory, the radiation forces and the trap stiffness on Rayleigh dielectric sphere induced by a focused Laguerre-Gaussian correlated Schell-model (LGCSM) beam are theoretically studied in this paper.

Abstract: Based on the Rayleigh scattering theory, the radiation forces and the trap stiffness on Rayleigh dielectric sphere induced by a focused Laguerre–Gaussian correlated Schell-model (LGCSM) beam are theoretically studied. It is found that by choosing the appropriate transverse coherence width, mode orders, transverse beam width, and focus lengths, a Rayleigh particle whose refractive index is larger or smaller than the ambient medium can be trapped. Our results will have some theoretical reference value for optical trapping.

18 citations

##### Cited by

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KAIST

^{1}TL;DR: Kim et al. as discussed by the authors used a sharp tip of platinum-coated silicon to write a charged pattern with a density similar to that of commercially available electrets into a thin film of lanthanum manganite.

Abstract: Transition metal oxides (TMOs) are an important class of materials that show a wide range of functionalities involving spin, charge, and lattice degrees of freedom. The strong correlation between electrons in d-orbitals and the multivalence nature give rise to a variety of exotic electronic states ranging from insulator to superconductor and cause intriguing phase competition phenomena. Despite a burst of research on the multifarious functionalities in TMOs, little attention has been paid to the formation and integration of an electret—a type of quasi-permanent electric field generator useful for nanoscale functional devices as an electric counterpart to permanent magnets. Here, we find that an electret can be created in LaMnO3 thin films by tip-induced electric fields, with a considerable surface height change, via solid-state electrochemical amorphization. The surface charge density of the formed electret area reaches ~400 nC cm−2 and persists without significant charge reduction for more than a year. The temporal evolution of the surface height, charge density, and electric potential are systematically examined by scanning probe microscopy. The underlying mechanism is theoretically analyzed based on a drift-diffusion-reaction model, suggesting that positively charged particles, which are likely protons produced by the dissociation of water, play crucial roles as trapped charges and a catalysis to trigger amorphization. Our finding opens a new horizon for multifunctional TMOs. A material that generates its own electric field has been developed by scientists in South Korea. An electret is the electrical equivalent of a magnet in that it is formed of two electric poles rather than two magnetic poles. Just as magnetic dipoles give rise to permanent magnets, electret materials create a quasi-permanent electric field. They are useful for microphones, photocopiers and many other electrical devices. Yong-Jin Kim and Chan-Ho Yang from the Korea Advanced Institute of Science and Technology, Daejeon, have created an electret using transition metal oxides. The researchers used a sharp tip of platinum-coated silicon to “write” a charged pattern with a density similar to that of commercially available electrets into a thin film of lanthanum manganite. These patterns persisted for more than a year. An electret can be created in a complex transition metal oxide LaMnO3 by tip-induced electric fields with a considerable surface height change via solid-state electrochemical amorphization. The surface charge density of the formed electret area reaches ~400 nC cm−2 and persists without significant charge reduction for more than a year. Our finding opens a new horizon for multifunctional transition metal oxides by providing an electric counterpart to permanent magnets.

134 citations

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TL;DR: In this article, the generation of cylindrical vector beams in birefringent crystals is studied analytically and experimentally in paraxial and non-paraxial regimes.

Abstract: The generation of cylindrical vector beams in birefringent crystals is studied analytically and experimentally in paraxial and non-paraxial regimes. At sharp focusing (in the non-paraxial case), two foci corresponding ordinary and extraordinary beams are formed along the crystal’s axis. There is the radially polarized distribution in one focus and the azimuthally polarized distribution in the other focus when the incident beam has the vortex phase of the first order and circular polarization of the opposite direction. The results are extended to the generation of higher-order radially and azimuthally polarized laser beams. The physical experiments with an Iceland spar crystal have been conducted.

59 citations

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TL;DR: GSM vortex beams is less affected by turbulence than GSM non-vortex beams under certain condition, and will be useful in long-distance free-space optical communications.

Abstract: Based on the extended Huygens-Fresnel principle and the definition of second-order moments of the Wigner distribution function (WDF), the analytical expressions for the propagation factors (M2-factors) and Strehl ratio SR of the Gaussian Schell-model (GSM) vortex beams and GSM non-vortex beams propagation through non-Kolmogorov atmospheric turbulence are derived, and used to study the influence of non-Kolmogorov atmospheric turbulence on beam quality of the GSM vortex beams. It is shown that the smaller the generalized structure constant and the outer scale of turbulence are, and the bigger the inner scale of turbulence is, the smaller the normalized propagation factor is, the bigger the Strehl ratio is, and the better the beam quality of GSM vortex beams in atmospheric turbulence is. The variation of beam quality with the generalized exponent α is nonmonotonic, when α = 3.11, the beam quality of the GSM vortex beams is the poorest through non-Kolmogorov atmospheric turbulence. GSM vortex beams is less affected by turbulence than GSM non-vortex beams under certain condition, and will be useful in long-distance free-space optical communications.

43 citations

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TL;DR: The field of spatially-structured light has seen an explosion in activity over the past decades, powered by technological advances for generating such light, and driven by questions of fundamental science as well as engineering applications.

Abstract: Research on spatially-structured light has seen an explosion in activity over the past decades, powered by technological advances for generating such light, and driven by questions of fundamental science as well as engineering applications. In this review we highlight work on the interaction of vector light fields with atoms, and matter in general. This vibrant research area explores the full potential of light, with clear benefits for classical as well as quantum applications.

40 citations

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01 Jan 2020TL;DR: This review covers broadly employed, currently developing, and yet untapped practical outcomes of optical coherence theory used in other fields of science, technology, and medicine.

Abstract: Over the last century, classical optical coherence has developed from a few vaguely related concepts into a standing along branch of optics and, more broadly, electromagnetics, that has resulted in a number of groundbreaking discoveries concerning the nature of light, its evolution and interaction with matter. While the theoretical developments of this field have been well documented in a number of excellent monographs and review articles, its applications have never been properly summarized. In this review we cover broadly employed, currently developing, and yet untapped practical outcomes of optical coherence theory used in other fields of science, technology, and medicine.

34 citations