Publications by authors named "Qiwen Zhan"

It is generally recognized that there is only a single optical potential-well near the focus in optical traps with a focused Gaussian beam. In this work, we show that this classic Gaussian-beam optical trap has additional optical potential-wells for optical manipulation at the subwavelength scale in the off-focus transverse plane. The additional optical potential-wells are formed by the synergy of both the gradient trapping force and the transverse scattering force, though in previous studies the scattering force usually has adverse effect such as reducing trapping stability.

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We propose and demonstrate an ultra-wide tunable mode-locked all-fiber laser based on nonlinear amplifying loop mirror (NALM) with the output of cylindrical vector beams (CVBs). The tuning range covers from 1029 nm to 1098 nm through the intracavity nonlinear polarization evolution (NPE) filter effect. The switchable CVBs between radially and azimuthally polarized beams with mode purity above 90% are generated by incorporating a broadband few-mode long-period fiber grating (LPFG).

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In recent years, research on chiral bound states in the continuum (BIC) has surged, leading to the development of various chiral metasurfaces with narrow bandwidths by breaking of in-plane and out-of-plane symmetries. However, the ability to dynamically tune the working band remains relatively unexplored, which is valuable for chiral sensing applications. Optical phase-change materials, with tunable dielectric constants and switchable properties during phase transition, offer the potential for dynamic control of optical metasurfaces.

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Structured beams carrying orbital angular momentum (OAM) provide powerful capabilities for applications in optical tweezers, super-resolution imaging, quantum optics, and ad-vanced microparticle manipulation. However, it is challenging for generate and control the OAM beams at the extreme ultraviolet (EUV) region due to the lack of suitable wave front shaping optics arise from being limited to the strong absorption of most materials. Here, we use a modified Fermat-spiral photon-sieve splitter to simultaneously generate two focused doughnut beams with opposite helical phase.

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Optical skyrmions, which are topological quasi-particles with nontrivial electromagnetic textures, have garnered escalating research interest recently for their potential in diverse applications. In this paper, we present a method for generating tightly focused optical skyrmion and meron topologies formed by electric-field vectors under 4-focusing system, where both the topology types (including Néel-, Bloch-, intermediate- and anti-skyrmion/meron) and the normal direction of the two-dimensional topology projection plane can be tailored at will. By utilizing time-reversal techniques, we analytically derive the radiation pattern of a multiple concentric-ring array of dipoles (MCAD) to obtain the required illumination fields on the pupil planes of the two high numerical aperture lenses.

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In structured light tweezers, it is a challenging technical issue to realize the complete circular motion of the trapped particles parallel to the optical axis. Herein, we propose and generate a novel optical skipping rope via combining beam shaping technology, Fourier shift theorem, and beam grafting technology. This optical skipping rope can induce the transverse orbital angular momentum (OAM) (i.

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Sophisticated infrared detection technology, operating through atmospheric transmission windows (usually between 3 and 5 μm and 8-13 μm), can detect an object by capturing its emitted thermal radiation, posing a threat to the survival of targeted objects. As per Wien's displacement law, the shift of peak wavelength towards shorter wavelengths as blackbody temperature rises, underscores the significance of the 3-5 μm range for ultra-high temperature objects (e.g.

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The vector vortex beams (VVBs) are endowed with helical phase and vector polarization. The rich optical properties of VVBs have attracted extensive concern. Here the geometric phase is applied to manipulate both the phase and polarization of light for switchable generation of VVBs by vortex plates.

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The magneto-optical Kerr effect (MOKE), as one of the magneto-optical effects, exhibits polarization change upon reflection that can be used to explore the internal information of magnetic materials with broad applications in modern information technology. However, typically, MOKE is quite weak due to the lower magneto-optical interaction. To tremendously enhance the MOKE, quasi-bound states in the continuum in a one-dimensional Ce- doped YFeO (CeYIG) film photonic crystal slabs (PCS) are proposed to improve the magneto-optical interaction in this work.

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Spatiotemporal structured light has opened up new avenues for optics and photonics. Current spatiotemporal manipulation of light mostly relies on phase-only devices such as liquid crystal spatial light modulators to generate spatiotemporal optical fields with unique photonic properties. However, simultaneous manipulation of both amplitude and phase of the complex field for the spatiotemporal light is still lacking, limiting the diversity and richness of achievable photonic properties.

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The complex external environment, such as obstruction and turbulence, poses significant limitations on the applications of rotational Doppler detection. The active manipulation of randomly fluctuated light has been proven effective in mitigating external environmental perturbations. Here, as an example, a partially coherent source with petal-like focal (or far) field distribution is constructed specifically for detecting rotational Doppler frequency shifts.

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Article Synopsis
  • This research investigates optical spatiotemporal vortices with transverse photon orbital angular momentum, focusing on spatiotemporal Laguerre-Gaussian (STLG) wavepackets that display unique topological features.
  • The study highlights the differences between conventional optical vortices and STLG wavepackets, which carry a composite transverse OAM with two opposing components.
  • Additionally, the research demonstrates a method for converting STLG wavepackets to ST Hermite-Gaussian (STHG) wavepackets, paving the way for advancements in quantum information, photonic topology, and various wave applications.
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Article Synopsis
  • The study introduces a method to control the orientation and topological charge of orbital angular momentum (OAM) in optical vortices using a specialized 4π focusing system.
  • This involves creating a continuous wave illumination by combining the pattern of a single dipole with a spiral phase factor.
  • The ability to manipulate OAM is shown to be achievable by adjusting the dipole's oscillation and the spiral phase, with potential applications in areas like optical trapping and light-matter interactions.
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With the characteristics of ultrasmall, ultrafast, and topological protection, optical skyrmions are great prospects for applications in high intensity data stroage, high resolution microscopic imaging, and polarization sensing. Flexible control over the topology of optical skyrmions is required for practical implementation/application. At present, the manipulation of optical skyrmions usually relies upon the change of spatial structure, which results in a limited-tuning range and a discontinuous control in the parameter space.

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Solvent-controlled extraction and precipitation are the most fundamental methods for obtaining hemicellulose from lignocellulosic biomass and purification processes. However, the dissolution and precipitation mechanisms involved have scarcely been mentioned. In this study, the molecular scale behavior of xylan-type hemicellulose during solvent-controlled extraction and precipitation is investigated using molecular dynamics (MD) simulations and density functional theory (DFT) calculations.

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Article Synopsis
  • Partially coherent light fields exhibit more stable intensity distributions compared to coherent light, but their practical application has been limited by measurement challenges.
  • A new method for decomposing these light fields is introduced, enabling researchers to analyze their properties and structure, including average intensity and cross-spectral density.
  • This technique demonstrates the potential for advancements in fields like optical imaging, encryption, and improved communication through complex environments.
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Coherent coupling of optical modes with a high Q-factor underpins realization of efficient light-matter interaction with multi-channels in resonant nanostructures. Here we theoretically studied the strong longitudinal coupling of three topological photonic states (TPSs) in a one-dimensional topological photonic crystal heterostructure embedded with a graphene monolayer in the visible frequencies. It is found that the three TPSs can strongly interplay with one another in the longitudinal direction, enabling a large Rabi splitting (∼ 48 meV) in spectral response.

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We achieve high-resolution sorting of the orbital angular momentum (OAM) of light with two bespoke diffractive optical elements using the generalized spiral transformation. The experimental sorting finesse is 5.3, approximately two times better performance than what has been reported.

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Article Synopsis
  • Existing methods for measuring the orbital angular momentum of vortex beams are limited and only work for specific types.
  • This research introduces a simple and universal method that can analyze any vortex beam, regardless of its coherence or spatial mode, including various types like Gaussian or Laguerre-Gaussian beams.
  • The new method is easy to implement using a commercial angular gradient filter and has been shown to work through both theoretical and experimental validation.
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Here we propose a metasurface consisting of symmetry-broken dielectric tetramer arrays, which can generate polarization-selective dual-band toroidal dipole resonances (TDR) with ultra-narrow linewidth in the near-infrared region. We found, by breaking the C symmetry of the tetramer arrays, two narrow-band TDRs can be created with the linewidth reaching ∼ 1.5 nm.

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Article Synopsis
  • The study explores a new technique to enhance circular dichroism using specially designed plasmonic molecule structures that create strong optical chiral responses.
  • It identifies that the z-component of the electric dipole is the key mechanism in chiral scattering when these molecules interact with light at specific angles.
  • The efficiency of this technique is validated through matching numerical simulations with experimental findings, suggesting significant applications in spectroscopy for analyzing chiral substances in both physics and biology.
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  • Developing a sustainable method to process wheat straw is important for environmental conservation.
  • An acid biphasic system using 2-methyltetrahydrofuran (2-MeTHF) and dilute p-toluenesulfonic acid (p-TsOH) effectively separates cellulose, hemicellulose, and lignin with minimal cellulose loss.
  • The optimal conditions resulted in 95.69% cellulose retention, 57.18% lignin removal, and a high yield of hemicellulose-derived C5 sugars, along with significant furfural production during further processing.
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The high-order Poincaré sphere (PS) introduces a mapping whereby any vector beams with spatially homogeneous ellipticity are represented by a specific point on the surface of the sphere. We propose the quantitative detection of high-order PS beams by introducing three sets of nonuniform polarization bases in the high-order Stokes parameters. Overall polarization detection is realized by directly separating and measuring the respective intensity of different nonuniform polarization bases based on S-plate.

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Photonic skyrmions and merons are topological quasiparticles characterized by nontrivial electromagnetic textures, which have received increasing research attention recently, providing novel degree of freedom to manipulate light-matter interactions and exhibiting excellent potential in deep-subwavelength imaging and nanometrology. Here, the topological stability of photonic spin meron lattices, which indicates the invariance of skyrmion number and robustness of spin texture under a continuous deformation of the field configuration, is demonstrated by inducing a perturbation to break the C symmetry in the presence spin-orbit coupling in an optical field. We revealed that amplitude perturbation would result in an amplitude-dependent shift of spin center, while phase perturbation leads to the deformation of domain walls, manifesting the metastability of photonic meron.

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Spatiotemporal optical vortices (STOVs) carrying transverse orbital angular momentum (OAM) are of rapidly growing interest for the field of optics due to the new degree of freedom that can be exploited. In this paper, we propose cylindrical vector two dimensional STOVs (2D-STOVs) containing two orthogonal transverse OAMs in both x-t and y-t planes for the first time, and investigate the tightly focusing of such fields using the Richards-Wolf vectorial diffraction theory. Highly confined spatiotemporal wavepackets with polarization structure akin to toroidal topology is generated, whose spatiotemporal intensity distributions resemble the shape of Yo-Yo balls.

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Synopsis of recent research by authors named "Qiwen Zhan"

  • - Qiwen Zhan's recent research primarily focuses on spatiotemporal manipulation of light and its applications in photonics, exploring techniques for controlling both amplitude and phase of light fields to enhance photonic properties.
  • - He has contributed significantly to the understanding and development of optical vortices with variable quantum numbers, and has advanced the detection of rotational Doppler shifts using specially constructed light sources, addressing issues posed by environmental interference.
  • - Additionally, Zhan's work extends into areas such as graphene plasmonics and the dynamics of optical skyrmions, emphasizing the potential for high-resolution applications in data storage, imaging, and polarization sensing through dynamic manipulation and strong coupling in topological photonic structures.

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