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(a) The −1st-order diffraction efficiency and the field distribution of a perfect diffraction metagrating in TM and TE polarization. (b) Intensity profile of TM and TE polarized quasi-Bessel beams steering with circular metagrating. (c), (d) 2D sweep by varying the incident wavelength and incident angle of a perfect diffraction metagrating in TM polarization and TE polarization, respectively.
Source publication
Bessel beams, with their non-diffractive property, have attracted great interest in recent years. Optical needle shaping of Bessel beams is highly desired in many applications, however, this typically requires low numerical aperture (NA) bulky 4f confocal systems incorporated with spatial light modulators or round filters. Here, we employ a circula...
Citations
... Gratings composed of periodic arrays of electrically thin wires can be regarded as metasurfaces or metagratings. When these arrays are placed on a metal-backed dielectric substrate, they can be used for manipulating EM waves across various frequency ranges-from microwaves [13,14] to visible frequencies [15,16]. This ability enables innovative approaches for controlling wave behavior, such as creating highimpedance surfaces [17,18], miniaturized patch antennas [19,20], and polarization converters [21,22]. ...
An analytical solution is derived for the problem of scattering of a plane E-polarized electromagnetic wave obliquely incident on a metagrating-like structure. The structure consists of a finite array of identical, thin, infinitely long, unloaded metallic cylindrical wires with circular cross-sections, in-plane-periodically arranged on the surface of a dielectric/ferrite layer backed by a conducting half-space. The ferrite layer is magnetized to saturation perpendicular to the direction of wave propagation. The solution is based on J.R. Wait’s earlier work on the problem of scattering of a plane E-polarized wave by a finite thin wire grating placed on a conducting half-space. Using long-wave approximations, expressions for the scattered electric field, total reflection coefficient, and far-field pattern are derived. The analysis of dependence of the reflection coefficient and far-field pattern depend on the angle of incidence and the strength of the DC bias magnetic field is also carried out in the study. It has been shown that a change in the layer magnetization results in a rearrangement of the scattered field pattern. The behavior of this rearrangement has been analyzed and discussed. The analytical results are validated at microwave frequencies through numerical simulations performed using electromagnetic software, confirming the accuracy of the proposed approach.
... Bessel beams, with long focal lengths and small focus diameters, are often used to handle structures with an aspect ratio of height to depth [21]. As a light with a needle-like distribution [22], Bessel beams are capable of cutting gold film at extremely fine widths and machining microholes in metal surfaces with a high depth to diameter ratio [23,24]. However, achieving widespread application of this method is impeded by the inherent challenges in attaining axial uniformity for experimentally obtained Bessel beams. ...
Antireflective microstructures fabricated using femtosecond laser possess wide-ranging applicability and high stability across different spectral bands. However, due to the limited aspect ratio of the focused light field, traditional femtosecond laser manufacturing faces challenges in efficiently fabricating antireflective microstructures with high aspect ratio and small period, which are essential for antireflection, on curved surfaces. In this study, we present a robust and efficient method for fabricating high-aspect-ratio and basal surface insensitive antireflective microstructures using a spatially shaped Bessel-like beam. Based on theoretical simulation, a redesigned telescopic system is proposed to flexibly equalize the intensity of the Bessel beam along its propagation direction, facilitating the fabrication of antireflective subwavelength structures on the entire convex lens. The fabricated microstructures, featuring a width of less than 2 µm and a depth of 1 µm, enhance transmittance from 75% to 85% on Diamond-ZnS composite material (D-ZnS) surfaces. Our approach enables the creation of high aspect ratio subwavelength structures with a z-position difference exceeding 600 µm. This practical, efficient, and cost-effective method is facilitated for producing antireflective surfaces on aero-optical components utilized in aviation.
Optical tweezers have been widely used for optical trapping and manipulating particles at the microscopic scale with a tightly focused laser beam. Over the recent years, optical fiber tweezers have attracted extensive attention due to their simple fabrication process, compact structure, strong anti-interference ability, convenient utilization, compatibility with chip devices, and flexible operation. In this review, the principle of optical force-based trapping is described, and the different fabrication methods of optical fiber tweezers are comprehensively discussed, including heating and pulling, chemical etching, grinding and polishing, coaxial splicing, photopolymer manufacturing, focused ion beam milling, and other emerging super-surface processing techniques. Then, the applications of such tweezers in optical manipulation, optical drive, optical transportation, optical imaging, and optical measurement are summarized. Finally, the future development prospects of optical fiber tweezers are presented.
