Generation of Optical Vortex Beams

Yang, Yuanjie; Qiu, Cheng‐Wei

doi:10.1002/9781119662945.ch7

Cited by 3 publications

(3 citation statements)

References 74 publications

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“…In fact, besides the integer OAM modes, the fractional-order OAM modes can be generated by a UCA, and the fractional-order vortex EM wave also satisfies the orthogonality in terms of the OAM mode [21][22][23][24][25]. The range of OAM modes for imaging can be expanded by utilizing fractional orders.…”

Section: Introductionmentioning

confidence: 99%

Three-Dimensional Imaging of Vortex Electromagnetic Wave Radar with Integer and Fractional Order OAM Modes

et al. 2023

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Vortex electromagnetic (EM) waves, with different orbital angular momentum (OAM) modes, have the ability to distinguish the azimuth of radar targets, and then the two-dimensional reconstruction of the targets can be achieved. However, the vortex EM wave imaging methods in published research have no ability to obtain the elevation of the targets, and thus, the three-dimensional spatial structure and richer feature information of the radar target cannot be obtained. Therefore, a three-dimensional imaging method of vortex EM waves with integer- and fractional-order OAM modes is proposed in this paper, which can realize a three-dimensional reconstruction of a radar target based on a uniform circular array (UCA) with two-step imaging. First, the vortex EM wave with integer- and fractional-order OAM modes is generated, and the echo model with different OAM mode types is established. Thereafter, the echo with integer order is processed to obtain the range-azimuth image by fast Fourier transform (FFT). Then, in order to realize the three-dimensional reconstruction, the echo with fractional order is processed by utilizing the butterfly operation and analyzing the characteristics of the fractional Bessel function. Moreover, the resolution and reconstruction precision of the azimuth and elevation are analyzed. Finally, the effectiveness of the proposed method is verified by simulation experiments.

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Section: Introductionmentioning

confidence: 99%

Three-Dimensional Imaging of Vortex Electromagnetic Wave Radar with Integer and Fractional Order OAM Modes

et al. 2023

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“…The methods used to generate vortex beams vary significantly (see, e.g., [26][27][28]). Currently, the most widely used devices for generating vortex beams are spatial light modulators (SLMs).…”

Section: Introductionmentioning

confidence: 99%

Terahertz Bessel Beams Formed by Binary and Holographic Axicons

et al. 2023

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The characteristics of high-power vortex Bessel beams in the terahertz range (λ=141 μm) obtained with the use of diffractive axicons (DAs) illuminated by a Gaussian beam of the Novosibirsk free-electron laser were studied. Two of the three possible types of DA recently described in our previous paper, namely, binary spiral silicon axicons (BAs), forming beams with a topological charge l equal to 0–4 and 9, and a diamond “holographic” axicon (HA), forming a beam with l=9, were used in the experiments. These axicons formed beams whose cross sections in the region of inner Bessel rings were close to those of ideal Bessel beams, but their intensities varied in azimuth with a frequency of l and 2l for the BAs and HA, respectively. However, in the case of the BAs, the beams had a pronounced helical structure at the periphery, whereas for the HA, the beam was axisymmetric. By focusing these beams with a lens, we studied the structure of the so-called “perfect” beams (PBs). While an ideal Bessel beam exhibits a PB as a thin ring, in the case of the BAs, we observed a broadened ring structure consisting of 2l short spirals, and for the HA, we observed a narrow ring with 2l maxima in azimuth. A comparison of the numerical calculations and experiments showed that the observed azimuthal intensity variations can be attributed to inaccuracies in the preparation of the axicon relief and/or discrepancies between the calculated and actual wavelengths, within a few percent. The results of this work enable the establishment of quality requirements for axicon manufacture and the appropriate selection of the axicon type in accordance with the requirements for the beam.

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“…Spatiotemporal optical vortices (STOVs) are light wave packets containing phase singularities that swirl around axes perpendicular to their direction of propagation and carry transverse orbital angular momentum in the spatiotemporal domain. − Unlike traditional vortex beams, − the phase vortices in STOVs evolve in both space and time, enabling new capabilities for integrated photonic chips and flat optics technology. However, conventional approaches relying on free-space optical components like spatial light modulators, lenses, and phased arrays , lack the integrability required for advanced photonic technologies.…”

mentioning

confidence: 99%

Exploiting Topological Darkness in Photonic Crystal Slabs for Spatiotemporal Vortex Generation

Liu,

Wang,

Tang

et al. 2024

Nano Lett.

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Spatiotemporal optical vortices (STOVs) with swirling phase singularities in space and time hold great promise for a wide range of applications across diverse fields. However, current approaches to generate STOVs lack integrability and rely on bulky free-space optical components. Here, we demonstrate routine STOV generation by harnessing the topological darkness phenomenon of a photonic crystal slab. Complete polarization conversion enforced by symmetry enables topological darkness to arise from photonic bands of guided resonances, imprinting vortex singularities onto an ultrashort reflected pulse. Utilizing time-resolved spatial mapping, we provide the first observation of STOV generation using a photonic crystal slab, revealing the imprinted STOV structure manifested as a curved vortex line in the pulse profile in space and time. Our work establishes photonic crystal slabs as a versatile and accessible platform for engineering STOVs and harnessing the topological darkness in nanophotonics.

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Generation of Optical Vortex Beams

Cited by 3 publications

References 74 publications

Three-Dimensional Imaging of Vortex Electromagnetic Wave Radar with Integer and Fractional Order OAM Modes

Three-Dimensional Imaging of Vortex Electromagnetic Wave Radar with Integer and Fractional Order OAM Modes

Terahertz Bessel Beams Formed by Binary and Holographic Axicons

Exploiting Topological Darkness in Photonic Crystal Slabs for Spatiotemporal Vortex Generation

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