- 标题
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- 实验方案
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Generation of polarization-sensitive modulated optical vortices with all-dielectric metasurfaces
摘要： Optical vortices (OVs) created from helical modes of light have extensive applications in optical manipulation, imaging and optical communications. Moreover, modulated optical vortices (MOVs) with modified wavefronts could provide new opportunities for fractionating particles and actuating microelectromechanical systems. Traditional devices for generating MOVs include spatial light modulators, spiral phase plates etc. However, such bulky devices are difficult to be applied to high-level integrated optical systems. Besides, other MOV generators are typically static and polarization-insensitive. Here, we proposed an all-dielectric metasurface to generate polarization-sensitive MOVs. The intensity patterns of the OVs can be modulated by adding a tangential modulation factor in the phase profile. Independent manipulation of two orthogonal polarizations was adopted via tailoring the geometric parameters of silicon (Si) pillars. We experimentally demonstrated that the metasurface could generate a doughnut and an actinomorphic vortex beams for different polarization inputs. In addition, the intensity pattern of the MOVs can be dynamically tuned by adjusting the polarization angle. This work can benefit optical manipulation and can be further extended to visible and near-infrared bands.
关键词： propagation phase,all-dielectric metasurfaces,mid-infrared,polarizations,modulated optical vortices
更新于2025-09-23 15:22:29
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Curves, wavefronts and caustics determined by the intensity pattern of an adiffractional beam
摘要： The aim of the present work is threefold, first we show that the intensity pattern of a nondiffracting beam determines an arbitrary positive real function and a complete integral of both the eikonal and Laplace equations on the plane; second, by using this result we associate to the intensity pattern a two-parameter family of curves and a one-parameter family of caustics on the plane and third, we use the intensity pattern of the Bessel beam of order m to identify its maxima with the family of caustics. This result suggests to define a family of caustics as the maxima of a given intensity pattern.
关键词： 070.3185 (Invariant optical fields),050.4865 (Optical vortices),080.0080 (Geometric optics)
更新于2025-09-19 17:15:36
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Optical Vortex Generation from an Anti-Resonant-Ring Picosecond Optical Parametric Oscillator
摘要： Optical vortices are beams with screw like (helical) phase variation along the propagation direction. This phase variation is given by exp(imθ) in the azimuthal plane, where m is the charge of optical vortices. Due to the doughnut shape intensity distribution and orbital angular momentum (OAM) content, optical vortices have found applications in various fields of science and technology. Commercially available mode converters transforming Gaussian beam into vortices suffer from the common drawback of low power handling capabilities and/or narrow wavelength coverage. To avoid such limitations, here we present a new technique of generating high power optical vortices over a wide wavelength range by using a Gaussian beam pumped anti-resonant-ring (ARR) optical parametric oscillator (OPO) [1]. By controlling the superposition of the Gaussian beams of an intracavity ARR, we have generated first-order HG modes [2] and further transformed into optical vortices using cylindrical lens [3], providing tunability across1457 nm to 1647 nm with an output power as high as 539 mW
关键词： optical parametric oscillator,optical vortices,orbital angular momentum,wavelength coverage,anti-resonant-ring
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Generation of Multiple Up-Converted OAM States from a Tunable Optical Vortex Parametric Laser Source
摘要： Optical vortices with a ring-shaped spatial form and an orbital angular momentum (OAM) of ?φ, arising from their helical wavefronts characterized by an azimuthal phase, exp(i?φ) (where ? is an integer termed the topological charge), have been widely exploiting a variety of research fields. These include optical trapping and manipulation, fluorescent microscopes with a high spatial resolution beyond the diffraction limit and materials processing. The aforementioned applications strongly desire wavelength-tunability and OAM-versatility to optical vortex sources. In this presentation, we report on the first generation of a signal output having multiple up-converted OAM states with ?(cid:3046) =3~5 (higher OAM than that of pump) from a nanosecond 2nd-order vortex (?(cid:3043) = 2) pumped singly resonant optical parametric oscillator (OPO) with a simple compact cavity configuration. The resulting idler exhibited negative OAM states with ?(cid:3036) =-1~-3.
关键词： Orbital angular momentum,OAM states,Wavelength-tunability,Optical vortices,Optical parametric oscillator
更新于2025-09-11 14:15:04
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Intense vortex high-order harmonics generated from laser-ablated plume
摘要： In this study, we demonstrate intense extreme-ultraviolet optical vortices generated using laser-ablation plume as the nonlinear medium. We used two types of plumes that are known to generate intense high-order harmonics for driving lasers with Gaussian beam profiles, but through different mechanisms, namely, carbon (diatomic carbon molecules) and tin (resonance with the autoionizing state). We find that the harmonic fluxes for diatomic carbon molecules are similar for Gaussian and vortex driving fields. However, for harmonics from the autoionizing state of tin (~26.3 eV), the enhancement factor of the resonant harmonic intensity decreases by ~50% when using the vortex driving field. The intense extreme-ultraviolet optical vortices demonstrated in this study will be useful for many applications including a material characterization technique known as optical angular momentum dichroism as well as the spectroscopy of spin-forbidden electronic transitions.
关键词： optical angular momentum dichroism,laser-ablation plume,spin-forbidden electronic transitions,extreme-ultraviolet optical vortices,high-order harmonics,diatomic carbon molecules,autoionizing state
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Phase Dislocations in the Negative Curvature Hollow Core Fibres
摘要： The negative curvature hollow core fibres (NCHCFs) have attracted recently a great deal of attention because of their potential for many practical applications ranging from optical communications to high power lasers and power delivery. In the NCHCFs light is strongly localized in the air core due to the mode field interaction with the limited portions of the core-cladding boundary. In our work we observed that the light leakage from the hollow core in NCHCFs has features which indicate the formation of phase dislocations and optical vortices in the cladding elements. Here we demonstrate that there are lines in the cladding capillary walls along which the imaginary and real parts of the transverse components of the core mode electric field Ex and Ey are equal to zero and can cross each other (the zero – amplitude lines). The direction of the transverse component of the core mode electric field is uncertain in the vicinity of these lines. Such behaviour of the core mode fields and its polarization indicates the presence of optical vortices in the cladding capillary wall.
关键词： negative curvature hollow core fibres,cladding capillary walls,phase dislocations,optical vortices
更新于2025-09-11 14:15:04
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Direct Generation of a Laguerre-Gaussian-Mode Optical Vortex Beam in a Single-Frequency Nd:YVO4 Unidirectional Ring Laser
摘要： A single-frequency, unidirectional ring laser with a ?rst order Laguerre-Gaussian (LG01) mode output end-pumped by using a ring-shaped pump beam is reported. This approach has been applied to a diode-pumped Nd:YVO4 laser in a traveling wave resonator con?guration yielding 2.1 W and 1.5 W of single-frequency LG01 mode outputs with helical wavefronts of left- and right-handedness, respectively. Moreover, we show that its wavefront helicity can be switched by changing the lasing direction and frequency. The selection mechanism of the wavefront helicity and the prospects of this approach are discussed.
关键词： Diode-pumped solid state lasers,Single-frequency laser,Optical vortices,Laguerre-Gaussian mode
更新于2025-09-11 14:15:04
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All-optical generation and ultrafast tuning of non-linear spin Hall current
摘要： Spin Hall effect, one of the cornerstones in spintronics refers to the emergence of an imbalance in the spin density transverse to a charge flow in a sample under voltage bias. This study points to a novel way for an ultrafast generation and tuning of a unidirectional nonlinear spin Hall current by means of subpicosecond laser pulses of optical vortices. When interacting with matter, the optical orbital angular momentum (OAM) carried by the vortex and quantified by its topological charge is transferred to the charge carriers. The residual spin-orbital coupling in the sample together with confinement effects allow exploiting the absorbed optical OAM for spatio-temporally controlling the spin channels. Both the non-linear spin Hall current and the dynamical spin Hall angle increase for a higher optical topological charge. The reason is the transfer of a higher amount of OAM and the enhancement of the effective spin-orbit interaction strength. No bias voltage is needed. We demonstrate that the spin Hall current can be all-optically generated in an open circuit geometry for ring-structured samples. These results follow from a full-fledged propagation of the spin-dependent quantum dynamics on a time-space grid coupled to the phononic environment. The findings point to a versatile and controllable tool for the ultrafast generation of spin accumulations with a variety of applications such as a source for ultrafast spin transfer torque and charge and spin current pulse emitter.
关键词： optical vortices,orbital angular momentum,Spin Hall effect,quantum rings,spin-orbit interaction,spintronics
更新于2025-09-10 09:29:36
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Vortex instability in turbulent free-space propagation
摘要： The spatial structuring of optical fields is integral within many next generation optical metrology and communication techniques. A verifiable physical model of the propagation of these optical fields in a turbulent environment is important for developing effective mitigation techniques for the modal degradation that occurs in a free-space link. We present a method to simulate this modal degradation that agrees with recently reported experimental findings. A 1.5 km free-space link is emulated by decomposing the optical turbulence that accumulates over a long distance link, into many, weakly perturbing steps of 10 m. This simulation shows that the high-order vortex at the centre of the helical phase profiles in modes that carry orbital angular momentum of ? are unstable and fracture into many vortices when they propagate over the link. This splitting presents issues for the application of turbulence mitigation techniques. The usefulness of pre-correction, post-correction, and complex field conjugation techniques are discussed.
关键词： optical propagation,orbital angular momentum,adaptive optics,optical vortices,atmospheric turbulence
更新于2025-09-09 09:28:46
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Vortex Dynamics and Optical Vortices || Optical Vortices Illumination Enables the Creation of Chiral Nanostructures
摘要： We discovered that optical vortices with an annular spatial form and an orbital angular momentum owing to a helical wave front enable us to twist materials, such as metal, silicon and azo-polymer, to form various structured matters including microneedles, chiral nanostructures and chiral surface reliefs. Such structured matters will potentially open the door to advanced devices, for instance, silicon photonic device, biomedical micro-electro-mechanical systems, ultrasensitive detector for chiral chemical composites and plasmonic metasurfaces for chiral chemical reactions.
关键词： chiral structured materials,singular optics,orbital angular momentum,laser materials processing,optical vortices
更新于2025-09-09 09:28:46