The ability to overcome the negative effects,induced by obstacles and turbulent atmosphere,is a core challenge of long-distance information transmission,and it is of great significance in free-space optical communicat...The ability to overcome the negative effects,induced by obstacles and turbulent atmosphere,is a core challenge of long-distance information transmission,and it is of great significance in free-space optical communication.The spatial-coherence structure,that characterizes partially coherent fields,provides a new degree of freedom for carrying information.However,due to the influence of the complex transmission environment,the spatial-coherence structure is severely damaged during the propagation path,which undoubtedly limits its ability to transmit information.Here,we realize the robust far-field orbital angular momentum(OAM)transmission and detection by modulating the spatial-coherence structure of a partially coherent vortex beam with the help of the cross-phase.The cross-phase enables the OAM information,quantified by the topological charge,hidden in the spatial-coherence structure can be stably transmitted to the far field and can resist the influence of obstructions and turbulence within the communication link.This is due to the self-reconstruction property of the spatial-coherence structure embedded with the cross-phase.We demonstrate experimentally that the topological charge information can be recognized well by measuring the spatial-coherence structure in the far field,exhibiting a set of distinct and separated dark rings even under amplitude and phase perturbations.Our findings open a door for robust optical signal transmission through the complex environment and may find application in optical communication through a turbulent atmosphere.展开更多
A phase-only method is proposed to transform an optical vortex field into desired spiral diffraction-interference patterns.Double-ring phase apertures are designed to produce a concentric high-order vortex beam and a ...A phase-only method is proposed to transform an optical vortex field into desired spiral diffraction-interference patterns.Double-ring phase apertures are designed to produce a concentric high-order vortex beam and a zeroth-order vortex beam,and the diffracted intensity ratio of two beams is adjustable between 0 and 1.The coherent superposition of the two diffracted beams generates a brighter Airy spot(or Poisson spot)in the middle of the spiral pattern,where the singularity for typical vortex beam is located.Experiments employing circular,triangular,and rectangular phase apertures with topological charges from 3 to 16 demonstrate a stable,compact,and flexible apparatus for vortex beam conversion.By adjusting the parameters of the phase aperture,the proposed method can realize the optical Gaussian tweezer function and the optical vortex tweezer function simultaneously along the same axis or switch the experimental setup between the two functions.It also has potential applications in light communication through turbulent air by transmitting an orbital angular momentum-coded signal with a concentric beacon laser.展开更多
Observation data of extreme gale in Capital Airport during 1976-2013 were analyzed,and climate characteristics of extreme gale in Capital Airport were summarized. Moreover,three extreme gale weather processes with lar...Observation data of extreme gale in Capital Airport during 1976-2013 were analyzed,and climate characteristics of extreme gale in Capital Airport were summarized. Moreover,three extreme gale weather processes with larger influences on December 10,2010,November 22,2011 and March 9,2013 were contrasted and analyzed,and results showed that extreme gale in Capital Airport mainly appeared during March-April or December-January. Occurrence frequency of extreme gale was the most from late afternoon to evening,and the minimum was from night to morning,while peak appeared during 14:00-15:00. Extreme gale of Capital Airport was dominated by northwest gale at the rear of cold front,and the peak occurred at the wind direction of 330°. The common effect of strong cold high pressure going south at the rear of ground cold front and highaltitude transverse trough turning vertical was main cause of extreme gale in Capital Airport,and momentum transmission below 500 hP a also had an important effect in the generation of extreme gale.展开更多
基金National Key Research and Development Program of China (2022YFA1404800,2019YFA0705000)National Natural Science Foundation of China (12104264,12192254,92250304,and 12374311)+2 种基金China Postdoctoral Science Foundation (2022T150392)Natural Science Foundation of Shandong Province (ZR2021QA014 and ZR2023YQ006)Qingchuang Science and Technology Plan of Shandong Province (2022KJ246).
文摘The ability to overcome the negative effects,induced by obstacles and turbulent atmosphere,is a core challenge of long-distance information transmission,and it is of great significance in free-space optical communication.The spatial-coherence structure,that characterizes partially coherent fields,provides a new degree of freedom for carrying information.However,due to the influence of the complex transmission environment,the spatial-coherence structure is severely damaged during the propagation path,which undoubtedly limits its ability to transmit information.Here,we realize the robust far-field orbital angular momentum(OAM)transmission and detection by modulating the spatial-coherence structure of a partially coherent vortex beam with the help of the cross-phase.The cross-phase enables the OAM information,quantified by the topological charge,hidden in the spatial-coherence structure can be stably transmitted to the far field and can resist the influence of obstructions and turbulence within the communication link.This is due to the self-reconstruction property of the spatial-coherence structure embedded with the cross-phase.We demonstrate experimentally that the topological charge information can be recognized well by measuring the spatial-coherence structure in the far field,exhibiting a set of distinct and separated dark rings even under amplitude and phase perturbations.Our findings open a door for robust optical signal transmission through the complex environment and may find application in optical communication through a turbulent atmosphere.
基金supported by the National Natural Science Foundation of China(Grant Nos.T2293753 and T2293750)the Major Science and Technology Project in Hainan Province of China(Grant No.ZDKJ2019012).
文摘A phase-only method is proposed to transform an optical vortex field into desired spiral diffraction-interference patterns.Double-ring phase apertures are designed to produce a concentric high-order vortex beam and a zeroth-order vortex beam,and the diffracted intensity ratio of two beams is adjustable between 0 and 1.The coherent superposition of the two diffracted beams generates a brighter Airy spot(or Poisson spot)in the middle of the spiral pattern,where the singularity for typical vortex beam is located.Experiments employing circular,triangular,and rectangular phase apertures with topological charges from 3 to 16 demonstrate a stable,compact,and flexible apparatus for vortex beam conversion.By adjusting the parameters of the phase aperture,the proposed method can realize the optical Gaussian tweezer function and the optical vortex tweezer function simultaneously along the same axis or switch the experimental setup between the two functions.It also has potential applications in light communication through turbulent air by transmitting an orbital angular momentum-coded signal with a concentric beacon laser.
文摘Observation data of extreme gale in Capital Airport during 1976-2013 were analyzed,and climate characteristics of extreme gale in Capital Airport were summarized. Moreover,three extreme gale weather processes with larger influences on December 10,2010,November 22,2011 and March 9,2013 were contrasted and analyzed,and results showed that extreme gale in Capital Airport mainly appeared during March-April or December-January. Occurrence frequency of extreme gale was the most from late afternoon to evening,and the minimum was from night to morning,while peak appeared during 14:00-15:00. Extreme gale of Capital Airport was dominated by northwest gale at the rear of cold front,and the peak occurred at the wind direction of 330°. The common effect of strong cold high pressure going south at the rear of ground cold front and highaltitude transverse trough turning vertical was main cause of extreme gale in Capital Airport,and momentum transmission below 500 hP a also had an important effect in the generation of extreme gale.
