While spin-orbit interaction has been extensively studied,few investigations have reported on the interaction between orbital angular momenta(OAMs).In this work,we study a new type of orbit-orbit coupling between the ...While spin-orbit interaction has been extensively studied,few investigations have reported on the interaction between orbital angular momenta(OAMs).In this work,we study a new type of orbit-orbit coupling between the longitudinal OAM and the transverse OAM carried by a three-dimensional(3D)spatiotemporal optical vortex(STOV)in the process of tight focusing.The 3D STOV possesses orthogonal OAMs in the x-y,t-x,and y-t planes,and is preconditioned to overcome the spatiotemporal astigmatism effect.x,y,and t are the axes in the spatiotemporal domain.The corresponding focused wavepacket is calculated by employing the Debye diffraction theory,showing that a phase singularity ring is generated by the interactions among the transverse and longitudinal vortices in the highly confined STOV.The Fourier-transform decomposition of the Debye integral is employed to analyze the mechanism of the orbit-orbit interaction.This is the first revelation of coupling between the longitudinal OAM and the transverse OAM,paving the way for potential applications in optical trapping,laser machining,nonlinear light-matter interactions,and more.展开更多
Harmonics generated by an intense femtosecond Gaussian laser pulse normally incident on a spiral-shaped thin foil target were studied. By using two-dimensional （2D） particle-in-cell （PIC） simulation, we observed e...Harmonics generated by an intense femtosecond Gaussian laser pulse normally incident on a spiral-shaped thin foil target were studied. By using two-dimensional （2D） particle-in-cell （PIC） simulation, we observed evident odd harmonics signals in the reflection direction and found that the reflected field has a helical structure determined by the target shape. This method provides a new way to generate an intense ultraviolet vortex with high-order topological charge by use of ultrahigh intense laser-driven harmonics.展开更多
Using an optical vortex coronagraph （OVC） is one of the most promising techniques for di- rectly imaging exoplanets because of its small inner working angle and high throughput. This paper presents the design and la...Using an optical vortex coronagraph （OVC） is one of the most promising techniques for di- rectly imaging exoplanets because of its small inner working angle and high throughput. This paper presents the design and laboratory demonstration performance of an OVC based on liquid crystal polymers （LCPs） at 633 nm and 1520 nm. The OVC can deliver good performance in laboratory tests and achieve a contrast of 10-6 at an angular distance of 3A/D, which can be implemented for imaging young giant exoplanets in combination with extreme adaptive optics.展开更多
The explosive growth of information urgently requires extending the capacity of optical communication and information processing.Orbital-angular-momentum-based mode division multiplexing(MDM)is recognized as the most ...The explosive growth of information urgently requires extending the capacity of optical communication and information processing.Orbital-angular-momentum-based mode division multiplexing(MDM)is recognized as the most promising technique to improve the bandwidth of a single fiber.To make it compatible with the dominant wavelength division multiplexing(WDM),broadband equal high-efficient phase encoding is highly pursued.Here,we propose a twisted-liquid-crystal and rear-mirror-based design for ultrabroadband reflective planar optics.The backtracking of the light inside the twisted birefringent medium leads to an achromatic phase modulation.With this design,a single-twisted reflective q-plate is demonstrated to convert a white beam to a polychromatic optical vortex.Jones calculus and vector beam characterization are carried out to analyze the broadband phase compensation.A dual-twisted configuration further extends the working band to over 600 nm.It supplies an ultrabroadband and reflective solution for the WDM/MDMcompatible elements and may significantly promote advances in ultrabroadband planar optics.展开更多
In order to generate high quality regular optical vortex array(OVA),we present an experimental method for generating OVA using phase only liquid crystal spatial light modulator(LC-SLM)assisted two gratings.In the sche...In order to generate high quality regular optical vortex array(OVA),we present an experimental method for generating OVA using phase only liquid crystal spatial light modulator(LC-SLM)assisted two gratings.In the scheme,holograms of two grating are displayed on the screen of two LC-SLMs respectively;the diffraction optical fields are captured by a CCD camera.The simulated and experimental results show that the regular OVA can be generated by using double diffraction gratings.The generated OVAs have a constant topological charge of±1.The method can provide a useful pathway to produce regular OVA for some applications in optical communication,particle trapping and optical metrology.展开更多
The generation of optical vortices from nonlinear photonic crystals(NPCs)with spatially modulated second-order nonlinearity offers a promising approach to extend the working wavelength and topological charge of vortex...The generation of optical vortices from nonlinear photonic crystals(NPCs)with spatially modulated second-order nonlinearity offers a promising approach to extend the working wavelength and topological charge of vortex beams for various applications.In this work,the second harmonic(SH)optical vortex beams generated from nonlinear fork gratings under Gaussian beam illumination are numerically investigated.The far-field intensity and phase distributions,as well as the orbital angular momentum(OAM)spectra of the SH beams,are analyzed for different structural topological charges and diffraction orders.Results reveal that higher-order diffraction and larger structural topological charges lead to angular interference patterns and non-uniform intensity distributions,deviating from the standard vortex profile.To optimize the SH vortex quality,the effects of the fundamental wave beam waist,crystal thickness,and grating duty cycle are explored.It is shown that increasing the beam waist can effectively suppress diffraction order interference and improve the beam’s quality.This study provides theoretical guidance for enhancing the performance of nonlinear optical devices based on NPCs.展开更多
Optical singularities are topological defects of electromagnetic fields;they include phase singularity in scalar fields,polarization singularity in vector fields,and three-dimensional(3D)singularities such as optical ...Optical singularities are topological defects of electromagnetic fields;they include phase singularity in scalar fields,polarization singularity in vector fields,and three-dimensional(3D)singularities such as optical skyrmions.The exploitation of photonic microstructures to generate and manipulate optical singularities has attracted wide research interest in recent years,with many photonic microstructures having been devised to this end.Accompanying these designs,scattered phenomenological theories have been proposed to expound the working mechanisms behind individual designs.In this work,instead of focusing on a specific type of microstructure,we concentrate on the most common geometric features of these microstructures—namely,symmetries—and revisit the process of generating optical singularities in microstructures from a symmetry viewpoint.By systematically employing the projection operator technique in group theory,we develop a widely applicable theoretical scheme to explore optical singularities in microstructures with rosette(i.e.,rotational and reflection)symmetries.Our scheme agrees well with previously reported works and further reveals that the eigenmodes of a symmetric microstructure can support multiplexed phase singularities in different components,such as out-of-plane,radial,azimuthal,and left-and right-handed circular components.Based on these phase singularities,more complicated optical singularities may be synthesized,including C points,V points,L lines,Néel-and bubble-type optical skyrmions,and optical lattices,to name a few.We demonstrate that the topological invariants associated with optical singularities are protected by the symmetries of the microstructure.Lastly,based on symmetry arguments,we formulate a so-called symmetry matching condition to clarify the excitation of a specific type of optical singularity.Our work establishes a unified theoretical framework to explore optical singularities in photonic microstructures with symmetries,shedding light on the symmetry origin of multidimensional and multiplexed optical singularities and providing a symmetry perspective for exploring many singularity-related effects in optics and photonics.展开更多
Spatiotemporal optical vortices(STOVs)have attracted significant attention for their unique properties.Recently,the second harmonic generation(SHG)of STOV pulses has been experimentally demonstrated,but the phase sing...Spatiotemporal optical vortices(STOVs)have attracted significant attention for their unique properties.Recently,the second harmonic generation(SHG)of STOV pulses has been experimentally demonstrated,but the phase singularity dynamics during this process remain elusive.Here,we theoretically investigate the separation and tilting of the phase singularities in STOVs during the SHG.Using the nonlinear Maxwell equation,we show that singularity separation is governed by group velocity mismatch,with accurate predictions provided by a Simpson-type integral under weak spatiotemporal walk-off conditions.In addition,paraxial wave equation analysis reveals that propagation induces singularity tilting,driven by spatial phase shifts.Our results not only offer deeper insights into the spatiotemporal coupling induced by complex nonlinear interactions but also reveal the underlying physical mechanisms in frequency up-conversion of space–time light pulses.展开更多
Taking two Laguerre-Gaussian beams with topological charge 1 = ±1 as an example, this paper studies the composite optical vortices formed by two noncollinear Laguerre-Gaussian beams with different phases, amplitu...Taking two Laguerre-Gaussian beams with topological charge 1 = ±1 as an example, this paper studies the composite optical vortices formed by two noncollinear Laguerre-Gaussian beams with different phases, amplitudes, waist widths, off-axis distances, and their propagation in free space. It is shown by detailed numerical illustrative examples that the number and location of composite vortices at the waist plane are variable by varying the relative phase β, amplitude ratio η, waist width ratio ξ, or off-axis distance ratio μ. The net topological charge lnet is not always equal to the sum lsum of charges of the two component beams. The motion, creation and annihilation of composite vortices take place in the free-space propagation, and the net charge during the propagation remains unchanged and equals to the net charge at the waist plane.展开更多
Propagation of light beams in turbid media such as underwater environments,fog,clouds,or biological tissues finds increasingly important applications in science and technology,including bio-imaging,underwater communic...Propagation of light beams in turbid media such as underwater environments,fog,clouds,or biological tissues finds increasingly important applications in science and technology,including bio-imaging,underwater communication,and free-space communication technologies.While many of these applications traditionally relied on conventional,linearly polarized Gaussian beams,light possesses many degrees of freedom that are still largely unexplored,such as spin angular momentum(SAM)and orbital angular momentum(OAM).Here,we present nonlinear light-matter interactions of such complex light beams with"rotational"degrees of freedom in engineered nonlinear colloidal media.By making use of both variational and perturbative approach,we consider non-cylindrical optical vortices,elliptical optical vortices,and higher-order Bessel beams integrated in time(HOBBIT)to predict the dynamics and stability of the evolution of these beams.These results may find applications in many scenarios involving light transmission in strongly scattering environments.展开更多
Optical vortices with tunable polarization states and topological charges are widely investigated in various physical systems and practical devices for high-capacity optical communication.However,this kind of structur...Optical vortices with tunable polarization states and topological charges are widely investigated in various physical systems and practical devices for high-capacity optical communication.However,this kind of structured light beams is usually generated using several polarization and spatial phase devices,which decreases the configurability of optical systems.Here,we have designed a kind of polarized optical multi-vortices generator based on the Stokes-Mueller formalism and cross-phase modulation.In our scheme,multi-channel generation of polarized vortex beams can be realized through a single optical element and a single-input Gaussian beam.The polarization states and orbital angular momentum of the generated light beams are all-optically controllable.Furthermore,the proposed polarized optical multi-vortices generator has also been demonstrated experimentally through one-step holographic recording in an azobenzene liquid-crystalline film and the experimental results agree with theoretical analysis.展开更多
We demonstrate an optical realization for the rotating BTZ black hole using the recent popular photon fluid model in an optical vortex but with a new proposed expression for the optical phase.We also give the numerica...We demonstrate an optical realization for the rotating BTZ black hole using the recent popular photon fluid model in an optical vortex but with a new proposed expression for the optical phase.We also give the numerical realization for the optical vortex to ensure that it can be generated experimentally.Different from the earlier suggestions for the analogue rotating black holes,our proposal includes an inner horizon in the analogue black hole structure.Such structure can keep for a long distance for the convenience of observing analogue Hawking or Penrose radiations.展开更多
Vortex beams carrying orbital angular momentum(OAM)are of great significance for high-capacity communication and super-resolution imaging.However,there is a huge gap between the free-space vortices(FVs)and plasmonic v...Vortex beams carrying orbital angular momentum(OAM)are of great significance for high-capacity communication and super-resolution imaging.However,there is a huge gap between the free-space vortices(FVs)and plasmonic vortices(PVs)on chips,and active manipulation as well as multiplexing in more channels have become a pressing demand.In this work,we demonstrate a terahertz(THz)cascaded metadevice composed of a helical plasmonic metasurface,a liquid crystal(LC)layer,and a helical dielectric metasurface.By spin-orbital angular momentum coupling and photon state superposition,PVs and FVs are generated with mode purity of over 85%on average.Due to the inversion asymmetric design of the helical metasurfaces,the parity symmetry breaking of OAM is realized(the topological charge numbers no longer occur in positive and negative pairs,but all are positive),generating 6 independent channels associated with the decoupled spin states and the near-/far-field positions.Moreover,by the LC integration,dynamic mode switching and energy distribution can be realized,finally obtaining up to 12 modes with a modulation ratio of above 70%.This active tuning and multi-channel multiplexing metadevice establishes a bridge connection between the PVs and FVs,exhibiting promising applications in THz communication,intelligent perception,and information processing.展开更多
Fractional optical vortices in the terahertz(THz)regime are supposed to have unique applications in various areas,i.e.,THz communications,optical manipulations,and THz imaging.However,it is still challenging to genera...Fractional optical vortices in the terahertz(THz)regime are supposed to have unique applications in various areas,i.e.,THz communications,optical manipulations,and THz imaging.However,it is still challenging to generate and manipulate high-power THz vortices.Here,we present a way to generate intense THz vortex beams with a continuously tunable topological charge by injecting a weakly relativistic ultrashort laser pulse into a parabolic plasma channel.By adjusting the injection conditions of the laser pulse,the trajectory of the laser centroid can be twisted into a cylindrical spiral,along which laser wakefields are also excited.Due to the inhomogeneous transverse density profile of the plasma channel and laser wakefield excitation,intense THz radiation carrying orbital angular momentum is produced with field strength reaching sub-GV/m,even though the drive laser energy is at a few tens of mJ.The topological charge of such a radiation is determined by the laser trajectories,which are continuously tunable as demonstrated by theoretical analysis as well as three-dimensional particle-in-cell simulations.Such THz vortices with unique properties may find applications in broad areas.展开更多
Spatiotemporal optical vortices(STOVs)are distinguished by their intricate phase structures and orbital angular momentum properties.This study demonstrates a coherent 4Pi-focused method generating STOV arrays by tight...Spatiotemporal optical vortices(STOVs)are distinguished by their intricate phase structures and orbital angular momentum properties.This study demonstrates a coherent 4Pi-focused method generating STOV arrays by tightly focusing the wave packets carrying spatiotemporal vortices and an additional spatial vortex.Numerical simulations reveal that the structural characteristics of the STOV array are governed by the interplay between the spatiotemporal and spatial topological charges of the incident wave packet.Notably,the introduction of spin angular momentum into the wave packet induces spin-orbit coupling,resulting in a distinctive tilt of the STOV array.These findings open potential pathways for high-dimensional optical manipulation and advanced optical information multiplexing.展开更多
An optical vortex beam has attracted significant attention across diverse applications,including optical manipulation,phase-contrast microscopy,optical communication,and quantum photonics.To utilize vortex generators ...An optical vortex beam has attracted significant attention across diverse applications,including optical manipulation,phase-contrast microscopy,optical communication,and quantum photonics.To utilize vortex generators for integrated photonics,researchers have developed ultra-compact vortex generators using fork gratings,metasurfaces,and integrated microcombs.However,those devices depend on costly,time-consuming nanofabrication and are constrained by the low signal-to-noise ratio due to the fabrication error.As an alternative maneuver,spin-orbit coupling has emerged as a method to obtain the vortex beam by converting spin angular momentum(SAM)without nanostructures.Here,we demonstrate the creation of an optical vortex beam using van der Waals(vdW)materials.The significantly high birefringence of vdW materials allows the generation of optical vortex beams,even with materials of sub-wavelength thickness.In this work,we utilize an 8µm-thick hexagonal boron nitride(hBN)crystal for the creation of optical vortices carrying topological charges of±2.We also present the generation of an optical vortex beam in a 320 nm-thick MoS_(2) crystal with a conversion efficiency of 0.09.This study paves the way for fabrication-less and ultracompact optical vortex generators,which can be applied for integrated photonics and large-scale vortex generator arrays.展开更多
The rapid development of optical technologies,including optical trapping,enhanced imaging,and microscopy,necessitates fundamentally new approaches to higher-dimensional optical beam shaping.We introduce a rigorous the...The rapid development of optical technologies,including optical trapping,enhanced imaging,and microscopy,necessitates fundamentally new approaches to higher-dimensional optical beam shaping.We introduce a rigorous theoretical approach for sculpting three-dimensional,topological particle-like objects,such as optical knots or links,including precise control of their individual parts.Universally applicable to knots created using braided zero lines,our method is validated through theoretical analysis and experimental measurements.The proposed approach enables new degrees of freedom in multi-dimensional singularities shaping,including rotations,shifts,and rescaling of their parts for enhanced stability in complex media.These results may find applications in the fields of three-dimensional optical trapping,manipulation,and subwavelength microscopy,as well as probing and imaging through atmospheric or underwater turbulence.展开更多
With their intricate vectorial structures in space,optical skyrmions have significantly expanded the landscape of topological optics and light-matter interactions.We theoretically investigate high harmonic generation ...With their intricate vectorial structures in space,optical skyrmions have significantly expanded the landscape of topological optics and light-matter interactions.We theoretically investigate high harmonic generation in crystals driven by optical skyrmions.We find that although the skyrmion number is not conserved,the resulting high-order harmonics can exhibit a distinctive multi-vortex structure,whose features are shaped by both the topology of the optical skyrmions and the rotational symmetry of the crystal.The position of the vortex centers can be effectively tuned by employing different types of optical skyrmions.To elucidate the underlying physics,we develop a multi-absorption channel model based on the conservation laws of spin and orbital angular momentum.Our work explores the role of optical topology in extreme nonlinear light-matter interactions,offering new opportunities for the formation and manipulation of optical vortices and novel structured light fields in the visible and ultraviolet regimes.展开更多
Spatial modes have received substantial attention over the last decades and are used in optical communication applications.In fiber-optic communications,the employed linearly polarized modes and phase vortex modes car...Spatial modes have received substantial attention over the last decades and are used in optical communication applications.In fiber-optic communications,the employed linearly polarized modes and phase vortex modes carrying orbital angular momentum can be synthesized by fiber vector eigenmodes.To improve the transmission capacity and miniaturize the communication system,straightforward fiber vector eigenmode multiplexing and generation of fiber-eigenmode-like polarization vortices(vector vortex modes)using photonic integrated devices are of substantial interest.Here,we propose and demonstrate direct fiber vector eigenmode multiplexing transmission seeded by integrated optical vortex emitters.By exploiting vector vortex modes(radially and azimuthally polarized beams)generated from silicon microring resonators etched with angular gratings,we report data-carrying fiber vector eigenmode multiplexing transmission through a 2-km large-core fiber,showing low-level mode crosstalk and favorable link performance.These demonstrations may open up added capacity scaling opportunities by directly accessing multiple vector eigenmodes in the fiber and provide compact solutions to replace bulky diffractive optical elements for generating various optical vector beams.展开更多
A high-efficiency technique for optical vortex(OV) generation is proposed and demonstrated. The technique is based on liquid crystal fork gratings with space-variant azimuthal orientations, which are locally controlle...A high-efficiency technique for optical vortex(OV) generation is proposed and demonstrated. The technique is based on liquid crystal fork gratings with space-variant azimuthal orientations, which are locally controlled via polarization-sensitive alignment layers. Thanks to the optical rewritability of the alignment agent and the dynamic image generation of the digital micro-mirror device, fork gratings can be instantly and arbitrarily reconfigured.Corresponding optical vortices carrying arbitrary azimuthal and radial indices are demonstrated with a conversion efficiency of 98.5%, exhibiting features of polarization control and electrical switching. The technique may pave a bright road toward OV generation, manipulation, and detection.展开更多
基金supported by the National Natural Science Foun-dation of China(12274299 and 92050202)the Shanghai Science and Technology Committee(22QA1406600).
文摘While spin-orbit interaction has been extensively studied,few investigations have reported on the interaction between orbital angular momenta(OAMs).In this work,we study a new type of orbit-orbit coupling between the longitudinal OAM and the transverse OAM carried by a three-dimensional(3D)spatiotemporal optical vortex(STOV)in the process of tight focusing.The 3D STOV possesses orthogonal OAMs in the x-y,t-x,and y-t planes,and is preconditioned to overcome the spatiotemporal astigmatism effect.x,y,and t are the axes in the spatiotemporal domain.The corresponding focused wavepacket is calculated by employing the Debye diffraction theory,showing that a phase singularity ring is generated by the interactions among the transverse and longitudinal vortices in the highly confined STOV.The Fourier-transform decomposition of the Debye integral is employed to analyze the mechanism of the orbit-orbit interaction.This is the first revelation of coupling between the longitudinal OAM and the transverse OAM,paving the way for potential applications in optical trapping,laser machining,nonlinear light-matter interactions,and more.
基金Project supported by the National Basic Research Program of China(Grant Nos.2013CBA01501 and 2013CBA01504)the National Key Scientific Instrument and Equipment Development Project,China(Grant No.2012YQ120047)+1 种基金CAS Key Program and National Natural Science Foundation of China(Grant Nos.11135012 and 11375262)a Project of Higher Educational Science and Technology Program of Shandong Province,China(Grant No.J11LA52)
文摘Harmonics generated by an intense femtosecond Gaussian laser pulse normally incident on a spiral-shaped thin foil target were studied. By using two-dimensional （2D） particle-in-cell （PIC） simulation, we observed evident odd harmonics signals in the reflection direction and found that the reflected field has a helical structure determined by the target shape. This method provides a new way to generate an intense ultraviolet vortex with high-order topological charge by use of ultrahigh intense laser-driven harmonics.
基金supported by the National Natural Science Foundation of China(Grant Nos.11661161011,11433007,11220101001,11328302 and 11373005)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA04075200)+2 种基金the International Partnership Program of Chinese Academy of Sciences(Grant Nos.114A32KYSB20160018 and 114A32KYSB20160057)the special fund for astronomy of CAS(2015–2016)Part of the work described in this paper was carried out at California State University,Northridge,with support from the Mt.Cuba Astronomical Foundation
文摘Using an optical vortex coronagraph （OVC） is one of the most promising techniques for di- rectly imaging exoplanets because of its small inner working angle and high throughput. This paper presents the design and laboratory demonstration performance of an OVC based on liquid crystal polymers （LCPs） at 633 nm and 1520 nm. The OVC can deliver good performance in laboratory tests and achieve a contrast of 10-6 at an angular distance of 3A/D, which can be implemented for imaging young giant exoplanets in combination with extreme adaptive optics.
基金supported by the National Key Research and Development Program of China(Grant No.SQ2022YFA1200117)the National Natural Science Foundation of China(Grant Nos.62035008,61922038,and 62005009)+1 种基金the Stable Support Fund of State Administration Science Technology and Industry or National Defense(Grant No.HTKJ2022KL504003)the Fundamental Research Funds for the Central Universities(Grant No.021314380189).
文摘The explosive growth of information urgently requires extending the capacity of optical communication and information processing.Orbital-angular-momentum-based mode division multiplexing(MDM)is recognized as the most promising technique to improve the bandwidth of a single fiber.To make it compatible with the dominant wavelength division multiplexing(WDM),broadband equal high-efficient phase encoding is highly pursued.Here,we propose a twisted-liquid-crystal and rear-mirror-based design for ultrabroadband reflective planar optics.The backtracking of the light inside the twisted birefringent medium leads to an achromatic phase modulation.With this design,a single-twisted reflective q-plate is demonstrated to convert a white beam to a polychromatic optical vortex.Jones calculus and vector beam characterization are carried out to analyze the broadband phase compensation.A dual-twisted configuration further extends the working band to over 600 nm.It supplies an ultrabroadband and reflective solution for the WDM/MDMcompatible elements and may significantly promote advances in ultrabroadband planar optics.
基金supported by the National Natural Science Foundation of China(Nos.61975099 and 11902317)the Natural Science Foundation of Shandong Province of China(Nos.ZR201702090137 and ZR2017LA010)。
文摘In order to generate high quality regular optical vortex array(OVA),we present an experimental method for generating OVA using phase only liquid crystal spatial light modulator(LC-SLM)assisted two gratings.In the scheme,holograms of two grating are displayed on the screen of two LC-SLMs respectively;the diffraction optical fields are captured by a CCD camera.The simulated and experimental results show that the regular OVA can be generated by using double diffraction gratings.The generated OVAs have a constant topological charge of±1.The method can provide a useful pathway to produce regular OVA for some applications in optical communication,particle trapping and optical metrology.
基金supported by the National Nat-ural Science Foundation of China(Nos.12192251,12174185,92163216,and 62288101).
文摘The generation of optical vortices from nonlinear photonic crystals(NPCs)with spatially modulated second-order nonlinearity offers a promising approach to extend the working wavelength and topological charge of vortex beams for various applications.In this work,the second harmonic(SH)optical vortex beams generated from nonlinear fork gratings under Gaussian beam illumination are numerically investigated.The far-field intensity and phase distributions,as well as the orbital angular momentum(OAM)spectra of the SH beams,are analyzed for different structural topological charges and diffraction orders.Results reveal that higher-order diffraction and larger structural topological charges lead to angular interference patterns and non-uniform intensity distributions,deviating from the standard vortex profile.To optimize the SH vortex quality,the effects of the fundamental wave beam waist,crystal thickness,and grating duty cycle are explored.It is shown that increasing the beam waist can effectively suppress diffraction order interference and improve the beam’s quality.This study provides theoretical guidance for enhancing the performance of nonlinear optical devices based on NPCs.
基金supported by the National Natural Science Foun-dation of China(62301596 and 62288101)Shaanxi Provincial Science and Technology Innovation Team(23-CX-TD-48)+4 种基金the KU Leuven internal funds:the C1 Project(C14/19/083)the Interdisciplinary Network Project(IDN/20/014)the Small Infrastructure Grant(KA/20/019)the Research Foundation of Flanders(FWO)Project(G090017N,G088822N,and V408823N)the Danish National Research Foundation(DNRF165).
文摘Optical singularities are topological defects of electromagnetic fields;they include phase singularity in scalar fields,polarization singularity in vector fields,and three-dimensional(3D)singularities such as optical skyrmions.The exploitation of photonic microstructures to generate and manipulate optical singularities has attracted wide research interest in recent years,with many photonic microstructures having been devised to this end.Accompanying these designs,scattered phenomenological theories have been proposed to expound the working mechanisms behind individual designs.In this work,instead of focusing on a specific type of microstructure,we concentrate on the most common geometric features of these microstructures—namely,symmetries—and revisit the process of generating optical singularities in microstructures from a symmetry viewpoint.By systematically employing the projection operator technique in group theory,we develop a widely applicable theoretical scheme to explore optical singularities in microstructures with rosette(i.e.,rotational and reflection)symmetries.Our scheme agrees well with previously reported works and further reveals that the eigenmodes of a symmetric microstructure can support multiplexed phase singularities in different components,such as out-of-plane,radial,azimuthal,and left-and right-handed circular components.Based on these phase singularities,more complicated optical singularities may be synthesized,including C points,V points,L lines,Néel-and bubble-type optical skyrmions,and optical lattices,to name a few.We demonstrate that the topological invariants associated with optical singularities are protected by the symmetries of the microstructure.Lastly,based on symmetry arguments,we formulate a so-called symmetry matching condition to clarify the excitation of a specific type of optical singularity.Our work establishes a unified theoretical framework to explore optical singularities in photonic microstructures with symmetries,shedding light on the symmetry origin of multidimensional and multiplexed optical singularities and providing a symmetry perspective for exploring many singularity-related effects in optics and photonics.
基金supported by the National Key Research and Development Program of China(Grant Nos.2023YFB3611000 and 2022YFA1405000)the National Natural Science Foundation of China(Grant Nos.62227821 and 62305157).
文摘Spatiotemporal optical vortices(STOVs)have attracted significant attention for their unique properties.Recently,the second harmonic generation(SHG)of STOV pulses has been experimentally demonstrated,but the phase singularity dynamics during this process remain elusive.Here,we theoretically investigate the separation and tilting of the phase singularities in STOVs during the SHG.Using the nonlinear Maxwell equation,we show that singularity separation is governed by group velocity mismatch,with accurate predictions provided by a Simpson-type integral under weak spatiotemporal walk-off conditions.In addition,paraxial wave equation analysis reveals that propagation induces singularity tilting,driven by spatial phase shifts.Our results not only offer deeper insights into the spatiotemporal coupling induced by complex nonlinear interactions but also reveal the underlying physical mechanisms in frequency up-conversion of space–time light pulses.
基金supported by the National Natural Science Foundation of China (Grant No 10574097)
文摘Taking two Laguerre-Gaussian beams with topological charge 1 = ±1 as an example, this paper studies the composite optical vortices formed by two noncollinear Laguerre-Gaussian beams with different phases, amplitudes, waist widths, off-axis distances, and their propagation in free space. It is shown by detailed numerical illustrative examples that the number and location of composite vortices at the waist plane are variable by varying the relative phase β, amplitude ratio η, waist width ratio ξ, or off-axis distance ratio μ. The net topological charge lnet is not always equal to the sum lsum of charges of the two component beams. The motion, creation and annihilation of composite vortices take place in the free-space propagation, and the net charge during the propagation remains unchanged and equals to the net charge at the waist plane.
基金support from the Office of Naval Research MURI(N00014-20-1-2550)。
文摘Propagation of light beams in turbid media such as underwater environments,fog,clouds,or biological tissues finds increasingly important applications in science and technology,including bio-imaging,underwater communication,and free-space communication technologies.While many of these applications traditionally relied on conventional,linearly polarized Gaussian beams,light possesses many degrees of freedom that are still largely unexplored,such as spin angular momentum(SAM)and orbital angular momentum(OAM).Here,we present nonlinear light-matter interactions of such complex light beams with"rotational"degrees of freedom in engineered nonlinear colloidal media.By making use of both variational and perturbative approach,we consider non-cylindrical optical vortices,elliptical optical vortices,and higher-order Bessel beams integrated in time(HOBBIT)to predict the dynamics and stability of the evolution of these beams.These results may find applications in many scenarios involving light transmission in strongly scattering environments.
基金Project supported by the National Natural Science Foundation of China (Grant No.92050116)。
文摘Optical vortices with tunable polarization states and topological charges are widely investigated in various physical systems and practical devices for high-capacity optical communication.However,this kind of structured light beams is usually generated using several polarization and spatial phase devices,which decreases the configurability of optical systems.Here,we have designed a kind of polarized optical multi-vortices generator based on the Stokes-Mueller formalism and cross-phase modulation.In our scheme,multi-channel generation of polarized vortex beams can be realized through a single optical element and a single-input Gaussian beam.The polarization states and orbital angular momentum of the generated light beams are all-optically controllable.Furthermore,the proposed polarized optical multi-vortices generator has also been demonstrated experimentally through one-step holographic recording in an azobenzene liquid-crystalline film and the experimental results agree with theoretical analysis.
文摘We demonstrate an optical realization for the rotating BTZ black hole using the recent popular photon fluid model in an optical vortex but with a new proposed expression for the optical phase.We also give the numerical realization for the optical vortex to ensure that it can be generated experimentally.Different from the earlier suggestions for the analogue rotating black holes,our proposal includes an inner horizon in the analogue black hole structure.Such structure can keep for a long distance for the convenience of observing analogue Hawking or Penrose radiations.
基金supported by the National Natural Science Foundation of China(62335012,62371258,624B2075,62205160,62435010)Young Scientific and Technological Talents in Tianjin(QN20230227)Fundamental Research Funds for the Central Universities,Nankai University(63231159).
文摘Vortex beams carrying orbital angular momentum(OAM)are of great significance for high-capacity communication and super-resolution imaging.However,there is a huge gap between the free-space vortices(FVs)and plasmonic vortices(PVs)on chips,and active manipulation as well as multiplexing in more channels have become a pressing demand.In this work,we demonstrate a terahertz(THz)cascaded metadevice composed of a helical plasmonic metasurface,a liquid crystal(LC)layer,and a helical dielectric metasurface.By spin-orbital angular momentum coupling and photon state superposition,PVs and FVs are generated with mode purity of over 85%on average.Due to the inversion asymmetric design of the helical metasurfaces,the parity symmetry breaking of OAM is realized(the topological charge numbers no longer occur in positive and negative pairs,but all are positive),generating 6 independent channels associated with the decoupled spin states and the near-/far-field positions.Moreover,by the LC integration,dynamic mode switching and energy distribution can be realized,finally obtaining up to 12 modes with a modulation ratio of above 70%.This active tuning and multi-channel multiplexing metadevice establishes a bridge connection between the PVs and FVs,exhibiting promising applications in THz communication,intelligent perception,and information processing.
基金upported by the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDA25050100 and XDA25010100)the National Natural Science Foundation of China(Grant Nos.12474428,12135009,11991073,and 11991074)the Science and Technology Commission of Shanghai Municipality(Grant Nos.22JC1401900 and 24ZR1436900).
文摘Fractional optical vortices in the terahertz(THz)regime are supposed to have unique applications in various areas,i.e.,THz communications,optical manipulations,and THz imaging.However,it is still challenging to generate and manipulate high-power THz vortices.Here,we present a way to generate intense THz vortex beams with a continuously tunable topological charge by injecting a weakly relativistic ultrashort laser pulse into a parabolic plasma channel.By adjusting the injection conditions of the laser pulse,the trajectory of the laser centroid can be twisted into a cylindrical spiral,along which laser wakefields are also excited.Due to the inhomogeneous transverse density profile of the plasma channel and laser wakefield excitation,intense THz radiation carrying orbital angular momentum is produced with field strength reaching sub-GV/m,even though the drive laser energy is at a few tens of mJ.The topological charge of such a radiation is determined by the laser trajectories,which are continuously tunable as demonstrated by theoretical analysis as well as three-dimensional particle-in-cell simulations.Such THz vortices with unique properties may find applications in broad areas.
基金supported by the National Natural Science Foundation of China(Nos.12274074 and 12134013)the Natural Science Foundation of Jiangsu Province(No.BK20242024)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX25_0437)。
文摘Spatiotemporal optical vortices(STOVs)are distinguished by their intricate phase structures and orbital angular momentum properties.This study demonstrates a coherent 4Pi-focused method generating STOV arrays by tightly focusing the wave packets carrying spatiotemporal vortices and an additional spatial vortex.Numerical simulations reveal that the structural characteristics of the STOV array are governed by the interplay between the spatiotemporal and spatial topological charges of the incident wave packet.Notably,the introduction of spin angular momentum into the wave packet induces spin-orbit coupling,resulting in a distinctive tilt of the STOV array.These findings open potential pathways for high-dimensional optical manipulation and advanced optical information multiplexing.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(RS-2024-00338048)(RS-2024-00414119)also supported by the Republic of Korea’s MSIT,under the Global Research Support Program in the Digital Field program)(RS-2024-00412644)+2 种基金supervised by the IITP(Institute of Information and Communications Technology Planning&Evaluation)and also supported by Culture,Sports and Tourism R&D Program through the Korea Creative Content Agency grant funded by the Ministry of Culture,Sports and Tourism in 2024(RS-2024-00332210)also Artificial Intelligence Graduate School Program(No.RS-2020-II201373,Hanyang University)supervised by the IITP,and under the artificial intelligence semiconductor support program to nurture the best talents(IITP-(2025)-RS-2023-00253914)grant funded by the Korea government,and by the MSIT(RS-2023-00261368,RS-2025-02218723,RS-2025-02283217).
文摘An optical vortex beam has attracted significant attention across diverse applications,including optical manipulation,phase-contrast microscopy,optical communication,and quantum photonics.To utilize vortex generators for integrated photonics,researchers have developed ultra-compact vortex generators using fork gratings,metasurfaces,and integrated microcombs.However,those devices depend on costly,time-consuming nanofabrication and are constrained by the low signal-to-noise ratio due to the fabrication error.As an alternative maneuver,spin-orbit coupling has emerged as a method to obtain the vortex beam by converting spin angular momentum(SAM)without nanostructures.Here,we demonstrate the creation of an optical vortex beam using van der Waals(vdW)materials.The significantly high birefringence of vdW materials allows the generation of optical vortex beams,even with materials of sub-wavelength thickness.In this work,we utilize an 8µm-thick hexagonal boron nitride(hBN)crystal for the creation of optical vortices carrying topological charges of±2.We also present the generation of an optical vortex beam in a 320 nm-thick MoS_(2) crystal with a conversion efficiency of 0.09.This study paves the way for fabrication-less and ultracompact optical vortex generators,which can be applied for integrated photonics and large-scale vortex generator arrays.
文摘The rapid development of optical technologies,including optical trapping,enhanced imaging,and microscopy,necessitates fundamentally new approaches to higher-dimensional optical beam shaping.We introduce a rigorous theoretical approach for sculpting three-dimensional,topological particle-like objects,such as optical knots or links,including precise control of their individual parts.Universally applicable to knots created using braided zero lines,our method is validated through theoretical analysis and experimental measurements.The proposed approach enables new degrees of freedom in multi-dimensional singularities shaping,including rotations,shifts,and rescaling of their parts for enhanced stability in complex media.These results may find applications in the fields of three-dimensional optical trapping,manipulation,and subwavelength microscopy,as well as probing and imaging through atmospheric or underwater turbulence.
基金supported by the National Natural Science Foundation of China (Grant Nos. 12234002, 92250303, 12474486, 12504301, and 12504396)the National Key Research and Development Program of China (Grant No. 2024YFA1612101)。
文摘With their intricate vectorial structures in space,optical skyrmions have significantly expanded the landscape of topological optics and light-matter interactions.We theoretically investigate high harmonic generation in crystals driven by optical skyrmions.We find that although the skyrmion number is not conserved,the resulting high-order harmonics can exhibit a distinctive multi-vortex structure,whose features are shaped by both the topology of the optical skyrmions and the rotational symmetry of the crystal.The position of the vortex centers can be effectively tuned by employing different types of optical skyrmions.To elucidate the underlying physics,we develop a multi-absorption channel model based on the conservation laws of spin and orbital angular momentum.Our work explores the role of optical topology in extreme nonlinear light-matter interactions,offering new opportunities for the formation and manipulation of optical vortices and novel structured light fields in the visible and ultraviolet regimes.
基金supported by the National Basic Research Program of China(973 Program)under grants 2014CB340004,2014CB340001 and 2014CB340003the National Natural Science Foundation of China(NSFC)under grants 11690031,61761130082,11574001,11774116,11274131,61222502,61575224 and 61622510+4 种基金the Royal Society-Newton Advanced Fellowshipthe National Program for Support of Top-notch Young Professionalsthe Program for New Century Excellent Talents in University(NCET-11-0182)the Program for HUST Academic Frontier Youth Team,the Project ROAM(H2020-ICT-2014-1—Contract Number:645361)the Project Cornerstone(EPSRC-EP/L021129/1)。
文摘Spatial modes have received substantial attention over the last decades and are used in optical communication applications.In fiber-optic communications,the employed linearly polarized modes and phase vortex modes carrying orbital angular momentum can be synthesized by fiber vector eigenmodes.To improve the transmission capacity and miniaturize the communication system,straightforward fiber vector eigenmode multiplexing and generation of fiber-eigenmode-like polarization vortices(vector vortex modes)using photonic integrated devices are of substantial interest.Here,we propose and demonstrate direct fiber vector eigenmode multiplexing transmission seeded by integrated optical vortex emitters.By exploiting vector vortex modes(radially and azimuthally polarized beams)generated from silicon microring resonators etched with angular gratings,we report data-carrying fiber vector eigenmode multiplexing transmission through a 2-km large-core fiber,showing low-level mode crosstalk and favorable link performance.These demonstrations may open up added capacity scaling opportunities by directly accessing multiple vector eigenmodes in the fiber and provide compact solutions to replace bulky diffractive optical elements for generating various optical vector beams.
基金sponsored by the 973 programs (Nos. 2011CBA00200 and 2012CB921803)the NSFC programs (Nos. 61490714, 11304151, 61435008, and 61225026)+2 种基金the Ph.D. Programs Foundation of the Ministry of Education of China (No.20120091120020)the support from the Program for Changjiang Scholars and Innovative Research Team in University (No.IRT13021)PAPD
文摘A high-efficiency technique for optical vortex(OV) generation is proposed and demonstrated. The technique is based on liquid crystal fork gratings with space-variant azimuthal orientations, which are locally controlled via polarization-sensitive alignment layers. Thanks to the optical rewritability of the alignment agent and the dynamic image generation of the digital micro-mirror device, fork gratings can be instantly and arbitrarily reconfigured.Corresponding optical vortices carrying arbitrary azimuthal and radial indices are demonstrated with a conversion efficiency of 98.5%, exhibiting features of polarization control and electrical switching. The technique may pave a bright road toward OV generation, manipulation, and detection.
