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Generation of pure Laguerre-Gaussian vector beams on the higher-order Poincaré sphere by hollow Gaussian beams through dielectric metasurfaces
摘要： It is a longstanding challenge for the extracavity generation of vector beams (VBs) to have pure Laguerre-Gaussian (LG) modes due to diffraction. Here we propose theoretically and realize experimentally the generation of pure LG VBs by using hollow Gaussian beams (HGBs) through q-plates. A general expression for the VB generated by the HGB with arbitrary polarization is derived. It is found that when the order of the HGB is two times the topological charge of the q-plate, the VB possesses a pure LG mode and that any desired polarization distribution on the higher-order Poincaré sphere can be realized by tuning the incident polarization. Further we implement the q-plates with dielectric metasurfaces and experimentally verify the theoretical results. The generated pure LG VB may find applications in the situations where high mode purity is required.
关键词： Vector beam,Laguerre-Gaussian mode,Diffraction,Metasurfaces,Pancharatnam-Berry phase,Hollow Gaussian beam
更新于2025-09-19 17:15:36
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Plasmene Metasurface Absorbers: Electromagnetic Hot Spots and Hot Carriers
摘要： Light-matter interactions are extremely important as they sustain life on Earth and can be tailored for diverse applications in areas such as solar energy conversion, chemical sensing, and information storage. One key process of these interactions is the absorption of photons. We demonstrate a novel material capable of absorbing up to 98% of incident visible light. The material comprises a thin sheet of a tightly-packed two-dimensional lattice of metal nanoparticles, called plasmene, supported by a thin (sub-wavelength) dielectric film deposited on top of a mirror. We demonstrate how the resulting metasurface absorbers are useful in surface-enhanced spectroscopy and in the generation of plasmonic hot carriers. These structures hold great promise for applications in structural color, sensing and photocatalysis.
关键词： plasmene,optical magnetic mode,hot carriers,perfect absorption,metasurfaces,Plasmonics
更新于2025-09-19 17:15:36
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Gap-Surface Plasmon Metasurfaces for Broadband Circular-to-Linear Polarization Conversion and Vector Vortex Beam Generation
摘要： The ability to control and manipulate the polarization state of light is of crucial importance in many modern optical applications ranging from quantum technologies to biomedical sciences. Here, an ultrathin quarter-wave plate (QWP) with a gap-surface plasmon metasurface is designed, fabricated, and experimentally demonstrated, allowing for broadband and efficient conversion between circular and linear polarizations with ≈85% average reflectance across a 200 nm wide bandwidth in the near-infrared range (750–950 nm). Based on the QWP design, a general method is further derived to generate vector vortex beams (VVBs) that possess spatially varied distributions of the polarization vector and carry specified orbital angular momentums by using space-variant QWP unit cells. The fabricated metasurface exhibits highly efficient VVB generation over a wavelength range from 750 to 950 nm, with average efficiencies of ≈72% and ≈68% for the right circularly polarized and left circularly polarized incident light, respectively. The developed approach allows compact, cost-effective, and high-performance polarization converters to be realized, paving the way for the ultimate miniaturization of optical devices with arbitrary control of light fields.
关键词： broadband,gap-surface plasmon metasurfaces,circular-to-linear conversion,vector vortex beams
更新于2025-09-19 17:15:36
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X-shaped chiral plasmonic nanostructured metasurfaces: A numerical study
摘要： In this paper, the author reports a numerical investigation of spectroscopic circular dichroism (CD) properties, near-field enhancement, and optical chirality near a chiral plasmonic nanostructured metasurface. The individual constituents of the metasurface consist of periodic X -shaped Au nanostructures on a glass substrate. The nanostructure is made of two overlapping nanorods, including one vertical nanorod and one tilted nanorod. Strong CD of the metasurface was observed and tunable upon rotation of the individual nanorods due to geometrical symmetry breaking. Near-field enhancement of up to 5 times and a large local optical chirality were found at a plane 20 nm above the X -shaped nanostructure. Electromagnetic modeling analysis provides valuable guidelines for designing alternative two-dimensional chiral metamaterials that have potential applications for enhanced molecule and chiral plasmon interaction.
关键词： Metasurfaces,Symmetry breaking,Chiral plasmonic nanostructures,Circular dichroism
更新于2025-09-19 17:13:59
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Plasmonic Metasurfaces Situated on Ultra-thin Carbon Nanomembranes
摘要： During the last decade, optical metasurfaces consisting of designed nanoresonators arranged in a planar fashion were successfully demonstrated to allow for the realization of a large variety of flat optical components. However, in common implementations of metasurfaces and metasurface-based devices, their flat nature is thwarted by the presence of a substrate of macroscopic thickness, which is needed to mechanically support the individual nanoresonators. Here, we demonstrate that Carbon Nanomembranes (CNMs) having nanoscale thickness can be used as a basis for arranging array of plasmonic nano-resonators into a metamembrane, allowing for the realization of genuinely flat optical devices. CNMs belong to the family of two-dimensional materials, and their thickness, mechanical, chemical, and electrical properties can be tailored by the choice of the molecular precursors used for their fabrication. We experimentally fabricate gold split-ring-resonator (SRR) metasurfaces on top of a free-standing CNM, which has a thickness of only about 1 nm and shows negligible interaction with the incident light field. For optical characterization of the fabricated SRR CNM metasurfaces, we perform linear-optical transmittance spectroscopy, revealing the typical resonance structure of an SRR metasurface. Furthermore, numerical calculations assuming free-standing SRR arrays are in excellent agreement with corresponding experimental transmittance spectra. We believe that our scheme offers a versatile solution for the realization of ultrathin, ultra lightweight metadevices, and may initiate various future research directions and applications including complex sensor technologies, conformal coating of complex topographies with functional metasurfaces, fast prototyping of multilayer metasurfaces, and studying the optical properties of effectively free-standing nanoparticles without the need for levitation schemes.
关键词： carbon nanomembranes,two-dimensional materials,nanoplasmonics,flat-optics,metasurfaces
更新于2025-09-19 17:13:59
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Negative Refraction in Time-Varying Strongly Coupled Plasmonic-Antennaa??Epsilon-Near-Zero Systems
摘要： Time-varying metasurfaces are emerging as a powerful instrument for the dynamical control of the electromagnetic properties of a propagating wave. Here we demonstrate an efficient time-varying metasurface based on plasmonic nano-antennas strongly coupled to an epsilon-near-zero (ENZ) deeply subwavelength film. The plasmonic resonance of the metal resonators strongly interacts with the optical ENZ modes, providing a Rabi level spitting of ～30%. Optical pumping at frequency ω induces a nonlinear polarization oscillating at 2ω responsible for an efficient generation of a phase conjugate and a negative refracted beam with a conversion efficiency that is more than 4 orders of magnitude greater compared to the bare ENZ film. The introduction of a strongly coupled plasmonic system therefore provides a simple and effective route towards the implementation of ENZ physics at the nanoscale.
关键词： time-varying metasurfaces,epsilon-near-zero,plasmonic nano-antennas,negative refraction,phase conjugation
更新于2025-09-19 17:13:59
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The investigation of the electromagnetic coupling effect in terahertz toroidal metasurfaces and metamaterials
摘要： We proposed and fabricated toroidal dipole (TD) metasurfaces(MSs) with a metamolecule of two coplanar U-shaped split ring resonators(USRRs) fabricated on polyimide substrate, and TD metamaterials (MMs) were the stacks of two TD MSs layers, whose frequencies, electromagnetic (EM) distributions and Q factor can be efficiently affected by the EM coupling effect in TD MSs/MMs. It was found that the resonances frequencies of TD MMs were shifted to lower frequencies due to the increase of inductance by the stacks of metallic layer. Meanwhile, the high-frequency TD resonance in TD MMs would be tailored by the periodicity. Considering the relation between TD resonances and the scattering power of TD (Ty), the Q factor depended highly on the value of Ty in the same metamolecule structure. The optimization in excitation of TD provide opportunity to further increase the Q-factor of metamaterial and pave a way for potential applications in terahertz sensor and other functional devices.
关键词： Toroidal dipole,Terahertz,Metamaterials,Metasurfaces
更新于2025-09-19 17:13:59
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Metal-graphene hybrid active chiral metasurfaces for dynamic terahertz wavefront modulation and near field imaging
摘要： Chiral metasurfaces can achieve giant chiral optical responses and have been expanded from the optical band to other electromagnetic bands. Here, we propose a new method for dynamic terahertz circular dichroism (CD) manipulation in metasurfaces. By introducing a patterned and electrically doped graphene into the metamirror consists of double layer C-shaped split ring resonators (SRRs), efficient terahertz CD modulation is observed. Since the electrical doping of graphene changes the absorption loss of the metasuface cavity, the structure shows switching between a chiral metasurface and an ordinary metal mirror, which can be seen as "on" and "off" states. The calculation results show an efficient modulation of the terahertz CD in a large dynamic range. In addition, we also use the new method to design two metasurfaces for dynamic terahertz wavefront modulation and near-field digital imaging, both of which show a high-performance electrical switching. This method provides a new way for the design of active terahertz devices based on metasurfaces, and also promotes the applications of terahertz chiral metasurfaces in high-speed wireless communication and dynamic imaging.
关键词： Chiral metasurfaces,terahertz,circular dichroism,near-field imaging,graphene,wavefront modulation
更新于2025-09-19 17:13:59
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Spoof plasmonic metasurfaces with catenary dispersion for two-dimensional wide-angle focusing and imaging
摘要： Despite tremendous efforts have been devoted to investigating the analogy between the surface plasmon polariton and its spoof counterparts, it remains elusive that a single thin spoof plasmonic metalens realize wide-angle focusing and wide field-of-view (FOV) imaging. Here, we propose a spoof plasmonic metasurface that can impart arbitrary phase with high transmittance, which is comprised of two-dimensional (2D) gradient spoof-insulator-spoof waveguides. With the developed catenary field and dispersion theory, their intrinsic physics are theoretically analyzed. As a proof of concept, a spoof plasmonic metalens with a thickness of 0.15λ has been elaborately designed and experimentally demonstrated for wide-angle (~170°) focusing and wide FOV (~40°) imaging. To the best of our knowledge, it is the first experimental demonstration of wide FOV imaging of a 2D object with single thin and planar metalens in the microwave regime. The proposed method offers a promising solution to compact cameras, integrated imaging, and detection systems.
关键词： catenary dispersion,microwave regime,spoof plasmonic metasurfaces,wide-angle focusing,wide FOV imaging
更新于2025-09-19 17:13:59
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Wavelength-decoupled geometric metasurfaces by arbitrary dispersion control
摘要： Conventional multicolor metaholograms suffer from the fundamental limitations of low resolution and irreducible noise because the unit structure functionality is still confined to a single wavelength. Here, we propose wavelength-decoupled metasurfaces that enables to control chromatic phase responses independently in a full range from 0 to 2π for each wavelength. The propagation phase associated with the geometric phase of rectangular dielectric nanostructures plays a critical role to embed a dual phase response into a single nanostructure. A multicolor metahologram is also demonstrated to verify the feasibility of our method that breaks through the fundamental constraints of conventional multicolor meta-holograms. Our approach can be extended to achieve complete control of chromatic phase responses in the visible for general dual-wavelength diffractive optical elements.
关键词： wavelength-decoupled,multicolor metaholograms,metasurfaces,chromatic phase responses,dielectric nanostructures
更新于2025-09-19 17:13:59