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Dark Plasmon Modes in Symmetric Gold Nanoparticle Dimers Illuminated by Focused Cylindrical Vector Beams
摘要： The plasmon hybridization model of electromagnetic coupling between plasmonic nanoparticles predicts the formation of lower energy “bonding” and higher energy “antibonding” modes in analogy with the quantum mechanical description of chemical bonding. For a symmetric metallic nanoparticle dimer excited by linearly polarized light, the hybridization picture predicts that in-phase coupling of the dipole moments is optically allowed, creating bright “modes”, whereas the out-of-phase coupling is dark due to the cancellation of the oppositely oriented dipole moments (in the quasistatic approximation). These bright modes are electric dipolar in nature and readily couple to scalar (i.e., linearly or circularly polarized) beams of light. We show that focused cylindrical vector beams, specifically azimuthally and radially polarized beams, directly excite dark plasmon modes in symmetric gold nanoparticle (AuNP) dimers at normal incidence. We use single-particle spectroscopy and electrodynamics simulations to study the resonance scattering of AuNP dimers illuminated by azimuthally and radially polarized light. The electric field distributions of the focused azimuthal or radial beams are locally polarized perpendicular or parallel to the AuNP dimer axis, but with opposite directions at each particle. Therefore, the associated combinations of single-particle dipole moments are out-of-phase, and the excitation (resonance) is of so-called “dark modes”. In addition, multipole expansion of the fields associated with each scattering spectrum shows that the vector beam excitation involves driving multipolar, e.g., magnetic dipolar and electric quadrupolar, modes, and that they even dominate the scattering spectra (vs electric dipole). This work opens new opportunities for investigating dark plasmon modes in nanostructures, which are difficult to selectively excite by conventional polarized light.
关键词： electrodynamics simulations,dark plasmon modes,plasmon hybridization,single-particle spectroscopy,gold nanoparticle dimers,cylindrical vector beams
更新于2025-09-23 15:21:21
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Nonequilibrium Magnetic Oscillation with Cylindrical Vector Beams
摘要： Magnetic oscillation is a generic property of electronic conductors under magnetic fields and widely appreciated as a useful probe of their electronic band structure, i.e. the Fermi surface geometry. However, the usage of the strong static magnetic field makes the measurement insensitive to the magnetic order of the target material. That is, the magnetic order is anyhow turned into a forced ferromagnetic one. Here we theoretically propose an experimental method of measuring the magnetic oscillation in a magnetic-order-resolved way by using the azimuthal cylindrical vector (CV) beam, an example of topological lightwaves. The azimuthal CV beam is unique in that, when focused tightly, it develops a pure longitudinal magnetic field. We argue that this characteristic focusing property and the discrepancy in the relaxation timescale between conduction electrons and localized magnetic moments allow us to develop the nonequilibrium analogue of the magnetic oscillation measurement. Our optical method would be also applicable to metals under the ultra-high pressure of diamond anvil cells.
关键词： Topological lightwaves,Magnetic oscillation,Cylindrical vector beams,Nonequilibrium measurement,Fermi surface geometry
更新于2025-09-23 15:21:21
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Photoactive Functional Soft Materials (Preparation, Properties, and Applications) || Photoinduced Liquid Crystal Domain Engineering for Optical Field Control
摘要： Liquid crystals (LCs) have attracted considerable attention due to their pronounced high optical anisotropy/transparency over a wide electromagnetic spectrum, high sensibility to various external field stimuli (such as electric/magnetic field, light irradiation, and heat) and strong capability for matter and electromagnetic field interactions. Thanks to their large birefringence and reconfigurable director (i.e. local optical axis) orientation, LCs have become one of the most attractive candidates for making optical devices requiring versatile functionalities. Particularly, liquid crystal display (LCD) holds a dominant position in the flat panel display market nowadays. Essentially, they are composed of a huge number of separate light intensity modulators in the visible range. In addition to amplitude, LCs can freely manipulate other spatial degrees of light, such as polarization and phase. Through specifical designing of the director distribution of LC domains, one could arbitrarily manipulate the optical field. Optical field control is a key requirement for optics and photonics. Structured light, also known as shaped light or tailored light, is a light beam that has customized intensity, polarization, and phase. Recently, specific beams including vortex beams, vector beams (VBs), and Airy beams have been studied intensively due to their fantastic properties and diverse applications in optical trapping, laser processing, high‐resolution imaging, etc. Generally, these beams can be directly generated from Gaussian beams by spatially manipulating the amplitude or phase of light. Such manipulations could be accomplished by lens or plates with specific curvature radius, photoresist masks, or metasurfaces with delicately designed structures. However, their optical characteristics are static once the respective device is fabricated, which severely restricts corresponding applications. Thanks to the electro‐optical tunability of LCs, structured LC domains make these devices dynamic and more efficient.
关键词： vector beams,Airy beams,photoalignment,vortex beams,optical field control,structured light,Liquid crystals
更新于2025-09-23 15:21:01
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Structured Light from Lasers
摘要： Structured light is derived from the ability to tailor light, usually referring to the spatial control of its amplitude, phase, and polarization. Although a venerable topic that dates back to the very first laser designs, structuring light at the source has seen an explosion in activity over the past decade, fuelled by a modern toolkit that exploits the versatility of diffractive structures, liquid crystals, metasurfaces/metamaterials, and exotic laser geometries, as well as a myriad of applications that range from imaging, microscopy, and laser material processing to optical communication. Here, the recent progress in creating and controlling structured light is reviewed, with particular emphasis on structuring light at the source: structured light lasers. The various design approaches, including pump shaping, cavity geometries, and the use of custom intracavity optical elements, implemented in a variety of lasers from microchip solutions to high-power fibers are covered in a tutorial style. The history and latest developments in the field are reviewed, elucidating the various structured light patterns that have been created from lasers, including orbital angular momentum and vector states of light. Finally, the present challenges and limitations are highlighted, along with comments on likely future trends.
关键词： optical modes,random lasers,topological lasers,orbital angular momentum,vector beams,structured light
更新于2025-09-19 17:13:59
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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 Vector Bessel Beams and their Application for Laser Microprocessing of Transparent Materials
摘要： Bessel beams are perfect candidates for laser microprocessing of transparent materials due to generation of high aspect ratio micro voids [1], and ability to control micro crack formation enables to efficiently cut them [2, 3]. The crack propagation direction is controlled by inducing asymmetry to beam profile [3], and allows ultra-fast glass cutting over non-straight lines. The laser-matter interaction of various nondiffracting beams is heavily investigated and their utilisation for laser microprocessing is soon to be expected. Vector beams that are more exotic than scalar counterparts and can have additional beneficial properties for micro-manufacturing of materials. For instance, vector Bessel beam has a doughnut shaped intensity profile with complex spatial distribution of polarisation and can be de-composed to two transverse polarisation intensity components [4]. In this work, we examine generation of vector Bessel beams using an axicon and an s-plate (Workshop of photonics) – radial polarization converter [5]. The s-plate allows generation of azimuthally or radially polarized beams while axicon converts it to nondifftracting Bessel vector beam. The polariser was used to separate its orthogonal polarisation components (Fig. 1). The proposed approach to generate these beams is beneficial for high energy beam systems because s-plate withstands ultrashort (fs-ps) high power pulses. To investigate their applicability to transparent material micro-fabrication we performed microprocessing of a glass with vector Bessel beams and were able to induce high aspect ratio volume modifications and micro cracks in transparent materials. Vector Bessel beams produces cylinder shaped material modifications of glass (Fig 2 a)) while the use of single polarisation component generates two parallel needle like material modification (Fig. 2 b)). By elongating the pulse duration to few ps we have observed micro crack formation extending perpendicular to the beam propagation direction and to two intensity peaks. (Fig. 2 c)). The produced modifications are investigated to increase the laser microprocessing quality and speed.
关键词： Bessel beams,laser microprocessing,transparent materials,axicon,vector beams,s-plate
更新于2025-09-12 10:27:22
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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) - Tailoring Second-Harmonic Generation in Plasmonic Radial Trimers using Cylindrical Vector Beams
摘要： Collective effects in assemblies of plasmonic nanostructures are attracting widespread interest. Such effects are governed by the interactions among the constituents of the overall structure, providing an alternative path to modify plasmon resonances [1]. A particularly interesting collective effect in these structures is the so-called dark plasmon mode, which has a net zero dipole moment and cannot be accessed using plane waves or linearly polarized light under normal incidence. An emerging way to excite collective dark modes in such structures is through the use of cylindrical vector beams (CVB) that exhibit inhomogeneous states of polarization such as azimuthal or radial polarizations [2,3]. The use of CVBs to excite collective nonlinear optical effects such as second-harmonic generation (SHG) in oligomers has started only recently [4]. Here, we demonstrate a similar possibility by tailoring SHG in plasmonic radial trimers using CVBs.
关键词： dark plasmon mode,second-harmonic generation,cylindrical vector beams,plasmonic nanostructures
更新于2025-09-12 10:27:22
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Mode manipulation based on few-mode fiber devices
摘要： In this paper, several kinds of few-mode fiber (FMF) based devices has been designed. Then an all-FMF mode-locked ring laser with carbon nanotubes was demonstrated with the generation of high purity cylindrical vector beams (CVBs).
关键词： few-mode fiber,cylindrical vector beams,Mode manipulation
更新于2025-09-12 10:27:22
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Switchable multiwavelength thulium-doped fiber laser with cylindrical vector beam emission
摘要： We experimentally demonstrate a switchable multiwavelength thulium-doped fiber laser with cylindrical vector beam (CVB) emission, which is the first report, to our best knowledge, on the generation of CVBs in a 2 μm wavelength band. The Sagnac loop filter, made up of a 50:50 coupler, a section of polarization-maintaining fiber and a polarization controller, serves as a periodical filter and accounts for the excitation of multiwavelength channels. The mode-selective coupler consisting of both tapered single-mode and four-mode fibers has been designed and fabricated as a mode converter from LP01 to LP11 mode with a purity of >80%. By adjusting the polarization controllers, laser outputs with 1–3 switchable wavelengths have been realized in the spectrum ranging from 1988–1998 nm. The laser could find miscellaneous applications in wavelength/mode-division multiplexing system, etc.
关键词： cylindrical vector beams (CVBs),thulium-doped fiber laser (TDFL),multiwavelength fiber laser,mode conversion
更新于2025-09-12 10:27:22
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High-order cylindrical vector beams with tunable topological charge up to 14 directly generated from a microchip laser with high beam quality and high efficiency
摘要： Large topological charge optical vortex beams carrying orbital angular momentum have potential applications on optical trapping, optical communication with high capacity, quantum information processing. However, the beam quality is degraded in vortex beams generated with spiral phase plates or resonator mirrors with defect spots and optical conversion efficiency in solid-state lasers is sacrificed by controlling the loss of resonator. It is a big challenge for generating high beam quality, high-order cylindrical vector beams with large topological charge in compact solid-state lasers. Here, high-order cylindrical vector beams [Laguerre-Gaussian (LG) modes with zero degree and order of l, LG0,l] with tunable topological charges up to 14 have been generated in an annular beam pumped Yb:YAG microchip laser by manipulating the pump power-dependent population inversion distribution. Efficient performance with optical efficiency of 17.5% has been achieved. The output power is 1.36 W for a vector-vortex laser with 14 topological charges. The pump power dependent wavelength tunable and dual-wavelength laser oscillation in vector-vortex beams has been observed by controlling the reabsorption loss at 1030 nm. Wavelength tunable, dual-wavelength (1030 and 1050 nm) laser oscillation has been achieved for vector-vortex beams with topological charges of 8, 9, and 10. The laser beam quality factor M2 close to the theoretical value (l + 1) has been achieved for LG0,l vector-vortex beams with tunable topological charges up to 14. This work provides a new effective method for generating large topological charge high-order cylindrical vector beams in solid-state microchip lasers with high efficiency and high beam quality.
关键词： orbital angular momentum,cylindrical vector beams,topological charge,Yb:YAG microchip laser,optical vortex beams
更新于2025-09-11 14:15:04
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A review of complex vector light fields and their applications
摘要： Vector beams, and in particular vector vortex beams, have found many applications in recent times, both as classical fields and as quantum states. While much attention has focused on the creation and detection of scalar optical fields, it is only recently that vector beams have found their place in the modern laboratory. In this review, we outline the fundamental concepts of vector beams, summarise the various approaches to control them in the laboratory, and give a concise overview of the many applications they have spurned.
关键词： hyper-entanglement,vector beams,vector vortex modes,hybrid entanglement,polarisation,spatial light modulators,geometric phase
更新于2025-09-10 09:29:36