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Margheri G, Del Rosso T. Tunable Device for Long Focusing in the Sub-THz Frequency Range Based on Fresnel Mirrors. MICROMACHINES 2024; 15:715. [PMID: 38930685 PMCID: PMC11206159 DOI: 10.3390/mi15060715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2024] [Revised: 05/21/2024] [Accepted: 05/24/2024] [Indexed: 06/28/2024]
Abstract
THz radiation has gained great importance due to its potential applications in a wide variety of fields. For this reason, continuous efforts have been made to develop technological tools for use in this versatile band of the electromagnetic spectrum. Here, we propose a reflecting device with long focusing performances in the sub-THz band, using a bimirror device in which the relative angle is mechanically adjusted with the displacement of one of the mirrors. Despite the simplicity of the setup, the performance of this device is satisfactory down to a frequency of 0.1 THz. Theory and experience confirm that the bimirror is capable of focusing 0.1 THz radiation with a 2× magnification of the maximum input intensity while maintaining a longitudinal full width at half maximum (FWHM) of about 6 mm, which is about 12 times the depth of focus of a cylindrical optical element of the same focal length. In the absence of suitable THz equipment, the invariance property of the Fresnel diffraction integral allowed the predicted behavior to be tested in the THz range using conventional equipment operating at visible frequencies.
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Affiliation(s)
- Giancarlo Margheri
- Institute for Complex Systems of National Council of Researches of Italy, Via Madonna del Piano, 50019 Sesto Fiorentino, Italy
| | - Tommaso Del Rosso
- Department of Physics, Pontifícia Universidade Católica do Rio de Janeiro, Rua Marques de São Vicente, Rio de Janeiro 22451-900, Brazil;
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2
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Hu H, Lin W, Ma X, Hu X, Wang X. Terahertz 3-D fast line-scanning imaging using 3-D printed devices. OPTICS EXPRESS 2024; 32:4111-4121. [PMID: 38297619 DOI: 10.1364/oe.511757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Accepted: 01/04/2024] [Indexed: 02/02/2024]
Abstract
This article presents a terahertz (THz) fast line-scanning imaging system with three-dimensional (3-D) focus-steering capability operating at 0.1 THz. The system comprises a 3-D printed rotating multi-prism plate and a dual-device structure consisting of a negative ridge pyramid and a column ridge pyramid. The simulation and experimental results demonstrate that the system generates a sheet-shaped diffraction-free beam with a projection distance of approximately 175 mm and a diffraction-free distance of approximately 200 mm. Moreover, the system maintains a resolution greater than 4 mm within the diffraction-free range. Furthermore, the proposed THz lens-less line-scanning imaging system enables 3-D scanning imaging within a set range of ±22°. The proposed approach can be extended to cover other frequencies within the THz range by appropriately adjusting the parameters. The system has the advantages of long working distance and long depth of field, making it a very attractive candidate for low-cost, easy-fabrication, and easy-adjustment solutions for the next generation of THz fast detection and imaging technology.
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3
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Margheri G, Del Rosso T. Long-Focusing Device for Broadband THz Applications Based on a Tunable Reflective Biprism. MICROMACHINES 2023; 14:1939. [PMID: 37893376 PMCID: PMC10609471 DOI: 10.3390/mi14101939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 10/11/2023] [Accepted: 10/14/2023] [Indexed: 10/29/2023]
Abstract
THz radiation has assumed great importance thanks to the efforts in the development of technological tools used in this versatile band of the electromagnetic spectrum. Here, we propose a reflective biprism device with wavelength-independent long-focusing performances in the THz band by exploiting the high thermo-mechanical deformation of the elastomer polydimethylsiloxane (PDMS). This deformation allows for achieving significant optical path modulations in the THz band and effective focusing. The surface of a PDMS layer is covered with a gold thin film acting as a heater thanks to its absorption of wavelengths below ~500 nm. An invariance property of the Fresnel integral has been exploited to experimentally verify the THz performances of the device with an ordinary visible laser source, finding excellent agreement with the theoretical predictions at 1 and 3 THz. The same property also allowed us to experimentally verify that the reflective biprism focus has a longitudinal extension much greater than that exhibited by a benchmark convex cylindrical mirror with the same optical power. The device is thermo-mechanically stable up to a heating power of 270 mW, although it might be potentially exploited at higher powers with minor degradation of the optical performances.
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Affiliation(s)
- Giancarlo Margheri
- Institute for Complex Systems of National Council of Researches of Italy, Separate Location of Sesto Fiorentino, Via Madonna del Piano, 50019 Sesto Fiorentino, Florence, Italy
| | - Tommaso Del Rosso
- Department of Physics, Pontifícia Universidade Católica do Rio de Janeiro, Rua Marques de São Vicente, Rio de Janeiro 22451-900, Brazil;
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4
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Vogliardi A, Ruffato G, Bonaldo D, Zilio SD, Romanato F. Silicon metaoptics for the compact generation of perfect vector beams in the telecom infrared. OPTICS LETTERS 2023; 48:4925-4928. [PMID: 37707938 DOI: 10.1364/ol.501239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Accepted: 08/27/2023] [Indexed: 09/15/2023]
Abstract
Perfect vortices have attracted considerable attention as orbital angular momentum (OAM) beams with customizable ring-like intensity distribution. More recently, the non-separable combination of perfect vortices with opposite OAMs and spins, yielding so-called perfect vector beams, has further expanded their applications in the fields of optical manipulation and imaging, high-resolution lithography, and telecommunications. Exploiting the combined manipulation of dynamic and geometric phases using silicon anisotropic metaunits, here we present the design, fabrication, and characterization of novel, to the best of our knowledge, dielectric metaoptics for the compact generation of perfect vector beams in the telecom infrared using a single metasurface. These devices pave the way to integrated optical architectures with applications in information and communication technologies in both the classical and quantum regimes.
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5
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Hu W, Xu Z, Jiang H, Liu Q, Yao Z, Tan Z, Ligthart LP. Image restoration algorithm for terahertz FMCW radar imaging. APPLIED OPTICS 2023; 62:5399-5408. [PMID: 37706856 DOI: 10.1364/ao.493964] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Accepted: 06/13/2023] [Indexed: 09/15/2023]
Abstract
The terahertz frequency modulation continuous-wave (THz FMCW) imaging technology has been widely used in non-destructive testing applications. However, THz FMCW real-aperture radar usually has a small depth of field and poor lateral resolution, thus restricting the high-precision imaging application. This paper proposes a 150-220 GHz FMCW Bessel beam imaging system, effectively doubling the depth of field and unifying the lateral resolution compared to the Gaussian beam quasi-optical system. Moreover, a THz image restoration algorithm based on local gradients and convolution kernel priors is proposed to eliminate further the convolution effect introduced by the Bessel beam, thereby enhancing the lateral resolution to 2 mm. It effectively improves the image under-restoration or over-restoration caused by the mismatch between the ideal and actual point spread function. The imaging results of the resolution test target and semiconductor device verify the advantages of the proposed system and algorithm.
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6
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Wang Z, Yao Y, Pan W, Zhou H, Chen Y, Lin J, Hao J, Xiao S, He Q, Sun S, Zhou L. Bifunctional Manipulation of Terahertz Waves with High-Efficiency Transmissive Dielectric Metasurfaces. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2205499. [PMID: 36494100 PMCID: PMC9896063 DOI: 10.1002/advs.202205499] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 11/13/2022] [Indexed: 05/25/2023]
Abstract
Multifunctional terahertz (THz) devices in transmission mode are highly desired in integration-optics applications, but conventional devices are bulky in size and inefficient. While ultra-thin multifunctional THz devices are recently demonstrated based on reflective metasurfaces, their transmissive counterparts suffer from severe limitations in efficiency and functionality. Here, based on high aspect-ratio silicon micropillars exhibiting wide transmission-phase tuning ranges with high transmission-amplitudes, a set of dielectric metasurfaces is designed and fabricated to achieve efficient spin-multiplexed wavefront controls on THz waves. As a benchmark test, the photonic-spin-Hall-effect is experimentally demonstrated with a record high absolute efficiency of 92% using a dielectric metasurface encoded with geometric phases only. Next, spin-multiplexed controls on circularly polarized THz beams (e.g., anomalous refraction and focusing) are experimentally demonstrated with experimental efficiency reaching 88%, based on a dielectric meta-device encoded with both spin-independent resonant phases and spin-dependent geometric phases. Finally, high-efficiency spin-multiplexed dual holographic images are experimentally realized with the third meta-device encoded with both resonant and geometric phases. Both near-field and far-field measurements are performed to characterize these devices, yielding results in agreement with full-wave simulations. The study paves the way to realize multifunctional, high-performance, and ultra-compact THz devices for applications in biology sensing, communications, and so on.
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Affiliation(s)
- Zhuo Wang
- State Key Laboratory of Surface Physics and Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education)Fudan UniversityShanghai200433P. R. China
| | - Yao Yao
- State Key Laboratory of Surface Physics and Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education)Fudan UniversityShanghai200433P. R. China
| | - Weikang Pan
- Shanghai Engineering Research Centre of Ultra Precision Optical ManufacturingDepartment of Optical Science and EngineeringSchool of Information Science and TechnologyFudan UniversityShanghai200433P. R. China
| | - Haoyang Zhou
- State Key Laboratory of Surface Physics and Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education)Fudan UniversityShanghai200433P. R. China
| | - Yizhen Chen
- Shanghai Engineering Research Centre of Ultra Precision Optical ManufacturingDepartment of Optical Science and EngineeringSchool of Information Science and TechnologyFudan UniversityShanghai200433P. R. China
| | - Jing Lin
- State Key Laboratory of Surface Physics and Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education)Fudan UniversityShanghai200433P. R. China
| | - Jiaming Hao
- Institute of optoelectronicsFudan UniversityShanghai200433P. R. China
| | - Shiyi Xiao
- Shanghai Institute for Advanced Communication and Data ScienceShanghai UniversityShanghai200444P. R. China
| | - Qiong He
- State Key Laboratory of Surface Physics and Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education)Fudan UniversityShanghai200433P. R. China
| | - Shulin Sun
- Shanghai Engineering Research Centre of Ultra Precision Optical ManufacturingDepartment of Optical Science and EngineeringSchool of Information Science and TechnologyFudan UniversityShanghai200433P. R. China
- Yiwu Research Institute of Fudan UniversityChengbei RoadYiwu CityZhejiang322000P. R. China
| | - Lei Zhou
- State Key Laboratory of Surface Physics and Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education)Fudan UniversityShanghai200433P. R. China
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Ivaškevičiūtė-Povilauskienė R, Kizevičius P, Nacius E, Jokubauskis D, Ikamas K, Lisauskas A, Alexeeva N, Matulaitienė I, Jukna V, Orlov S, Minkevičius L, Valušis G. Terahertz structured light: nonparaxial Airy imaging using silicon diffractive optics. LIGHT, SCIENCE & APPLICATIONS 2022; 11:326. [PMID: 36385101 PMCID: PMC9668966 DOI: 10.1038/s41377-022-01007-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 09/09/2022] [Accepted: 10/08/2022] [Indexed: 05/17/2023]
Abstract
Structured light - electromagnetic waves with a strong spatial inhomogeneity of amplitude, phase, and polarization - has occupied far-reaching positions in both optical research and applications. Terahertz (THz) waves, due to recent innovations in photonics and nanotechnology, became so robust that it was not only implemented in a wide variety of applications such as communications, spectroscopic analysis, and non-destructive imaging, but also served as a low-cost and easily implementable experimental platform for novel concept illustration. In this work, we show that structured nonparaxial THz light in the form of Airy, Bessel, and Gaussian beams can be generated in a compact way using exclusively silicon diffractive optics prepared by femtosecond laser ablation technology. The accelerating nature of the generated structured light is demonstrated via THz imaging of objects partially obscured by an opaque beam block. Unlike conventional paraxial approaches, when a combination of a lens and a cubic phase (or amplitude) mask creates a nondiffracting Airy beam, we demonstrate simultaneous lensless nonparaxial THz Airy beam generation and its application in imaging system. Images of single objects, imaging with a controllable placed obstacle, and imaging of stacked graphene layers are presented, revealing hence potential of the approach to inspect quality of 2D materials. Structured nonparaxial THz illumination is investigated both theoretically and experimentally with appropriate extensive benchmarks. The structured THz illumination consistently outperforms the conventional one in resolution and contrast, thus opening new frontiers of structured light applications in imaging and inverse scattering problems, as it enables sophisticated estimates of optical properties of the investigated structures.
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Affiliation(s)
| | - Paulius Kizevičius
- Department of Fundamental Research, Center for Physical Sciences and Technology, Saulėtekio av. 3, Vilnius, 10257, Lithuania
| | - Ernestas Nacius
- Department of Fundamental Research, Center for Physical Sciences and Technology, Saulėtekio av. 3, Vilnius, 10257, Lithuania
| | - Domas Jokubauskis
- Department of Optoelectronics, Center for Physical Sciences and Technology, Saulėtekio av. 3, Vilnius, 10257, Lithuania
| | - Kęstutis Ikamas
- Institute of Applied Electrodynamics & Telecommunications, Vilnius University, Saulėtekio av. 3, Vilnius, 10257, Lithuania
| | - Alvydas Lisauskas
- Institute of Applied Electrodynamics & Telecommunications, Vilnius University, Saulėtekio av. 3, Vilnius, 10257, Lithuania
- CENTERA Labs., Institute of High Pressure Physics PAS, ul. Sokolowska 29/37, Warsaw, 01-142, Poland
| | - Natalia Alexeeva
- Department of Optoelectronics, Center for Physical Sciences and Technology, Saulėtekio av. 3, Vilnius, 10257, Lithuania
| | - Ieva Matulaitienė
- Department of Organic Chemistry, Center for Physical Sciences and Technology, Saulėtekio av. 3, Vilnius, 10257, Lithuania
| | - Vytautas Jukna
- Department of Fundamental Research, Center for Physical Sciences and Technology, Saulėtekio av. 3, Vilnius, 10257, Lithuania
| | - Sergej Orlov
- Department of Fundamental Research, Center for Physical Sciences and Technology, Saulėtekio av. 3, Vilnius, 10257, Lithuania
| | - Linas Minkevičius
- Department of Optoelectronics, Center for Physical Sciences and Technology, Saulėtekio av. 3, Vilnius, 10257, Lithuania
- Institute of Photonics and Nanotechnology, Department of Physics, Vilnius University, Saulėtekio av. 3, Vilnius, 10257, Lithuania
| | - Gintaras Valušis
- Department of Optoelectronics, Center for Physical Sciences and Technology, Saulėtekio av. 3, Vilnius, 10257, Lithuania
- Institute of Photonics and Nanotechnology, Department of Physics, Vilnius University, Saulėtekio av. 3, Vilnius, 10257, Lithuania
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8
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Downes LA, Whiting DJ, Adams CS, Weatherill KJ. Rapid readout of terahertz orbital angular momentum beams using atom-based imaging. OPTICS LETTERS 2022; 47:6001-6004. [PMID: 37219157 DOI: 10.1364/ol.476945] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2022] [Accepted: 10/24/2022] [Indexed: 05/24/2023]
Abstract
We demonstrate the rapid readout of terahertz orbital angular momentum (OAM) beams using an atomic-vapor-based imaging technique. OAM modes with both azimuthal and radial indices are created using phase-only transmission plates. The beams undergo terahertz-to-optical conversion in an atomic vapor, before being imaged in the far field using an optical CCD camera. In addition to the spatial intensity profile, we also observe the self-interferogram of the beams by imaging through a tilted lens, allowing the sign and magnitude of the azimuthal index to be read out directly. Using this technique, we can reliably read out the OAM mode of low-intensity beams with high fidelity in 10 ms. Such a demonstration is expected to have far-reaching consequences for proposed applications of terahertz OAM beams in communications and microscopy.
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9
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Tu S, Peng J, Yang Z, Liu J, Wang K. Single optical element to generate a meter-scale THz diffraction-free beam. OPTICS EXPRESS 2022; 30:39976-39984. [PMID: 36298938 DOI: 10.1364/oe.471070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Accepted: 10/03/2022] [Indexed: 06/16/2023]
Abstract
Diffraction-free electromagnetic beam propagates in free space without change in its two-dimensional transverse profile. Elongating diffraction-free length can benefit the practical application of this beam. Here, we demonstrate that a THz diffraction-free beam with meter-scale length can be achieved by using only one optical element. By circumscribing the line-shape of spherical harmonic function on a traditional axicon, such optical element is designed, and then can be fabricated by 3D-printing technique. Simulated, experimental, and theoretical results all show that the diffraction-free length of generated beam is over 1000 mm. Further analysis based on Fourier optics theory indicates that the spatial frequency of this beam has a comb distribution, which plays a key role during the beam generation process. Moreover, such distribution also demonstrates the beam generated by our invented optical element is not the Bessel beam, but a new diffraction-free beam. It is believed that this meter-scale THz diffraction-free beam can be useful in a non-contact and non-destructive THz imaging system for large objects.
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10
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Lightman S, Porat O, Hurvitz G, Gvishi R. Vortex-Bessel beam generation by 3D direct printing of an integrated multi-optical element on a fiber tip. OPTICS LETTERS 2022; 47:5248-5251. [PMID: 36240334 DOI: 10.1364/ol.470924] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Accepted: 09/09/2022] [Indexed: 06/16/2023]
Abstract
Shaping light beams as they propagate out of the tips of optical fibers is a desired ability, as the light could be tailored for various applications in a miniaturized, integrated, and cost-effective manner. However, fabricating sophisticated refractive elements directly onto fibers is challenging. By using 3D-direct laser writing (3D-DLW), high-quality optical devices could be fabricated directly on top of the fiber's facet by the two-photon absorption process. Here, we demonstrate how a high-order Bessel beam carrying orbital angular momentum (OAM) could be generated by using this lithography process. The beam is shaped using an integrated micro-optical system that consists of a twisted axicon and parabolic lens in an adapted fiber configuration. This work provides the analysis and measurements of the generated beam, along with simulated predictions. The far-field pattern, at a distance of 2 mm from the fiber, was examined, and we have found that the size of the central ring remained nearly unchanged, as expected for this type of beam. The beam's OAM value was measured using either an interference pattern or a mode convertor. Furthermore, the near-field and far-field Bessel beam profiles were investigated simultaneously at various laser power values, reaching intensities of up to 3.8 MW/cm2. This work may pave the way for future integrated beam manipulation on fibers, enabling the use of higher laser outputs.
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11
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Hu W, Xu Z, Jiang H, Liu Y, Yao Z, Zhang K, Ligthart LP. High range resolution wideband terahertz FMCW radar with a large depth of field. APPLIED OPTICS 2022; 61:7189-7196. [PMID: 36256339 DOI: 10.1364/ao.465647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Accepted: 08/02/2022] [Indexed: 06/16/2023]
Abstract
Terahertz frequency modulation continuous wave (THz FMCW) imaging technology has been widely used in non-destructive testing (NDT) applications of non-metallic materials. However, THz FMCW real-aperture radar usually has a narrow bandwidth and small depth of field, thus restricting the application of THz FMCW NDT. In this paper, a wideband THz signal (220-500 GHz) generation method is proposed by time-division multiplexing. Moreover, a dual-band quasi-optical design with a large depth of field is proposed based on the THz Bessel beam, and a high-quality range profile is obtained. Especially, a signal fusion extended Fourier analysis algorithm without prior knowledge is proposed to further enhance the range profile accuracy, which improves the range resolution to 0.28 mm (λ/3, center frequency 360 GHz). The effectiveness and advantages of the proposed system are verified by artificially constructing composite materials.
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12
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Grachev YV, Kokliushkin VA, Petrov NV. Open-source 3D-printed terahertz pulse time-domain holographic detection module. APPLIED OPTICS 2022; 61:B307-B313. [PMID: 35201153 DOI: 10.1364/ao.444979] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 12/20/2021] [Indexed: 06/14/2023]
Abstract
We present a holographic detection module to measure the spatially resolved distribution of pulsed terahertz field in a single scan by a motorized translation stage, responsible for the time delay. All mounts of the optical elements of the module are easily reproduced by 3D printing and attached to the optical cage system. The latter greatly simplifies the measurement procedure, allowing the experimenter to move and adjust the detection system as a single device. The developed mounts are made universal and can be used in other setups. We have made 3D models available as open-source hardware. The module is based on an electro-optical detection scheme with wide-aperture ZnTe crystal, crossed polarizers, and a matrix photodetector. The validation of its operability was performed with two experiments to measure the spatial distribution of the unperturbed field from the generator and the vortex field formed by the spiral phase plate. Optical vortices with multiple topological charges of 2-4 were detected on spectral components in the range from 0.3 to 1.1 THz. In addition, we have detailed the alignment process of terahertz imaging systems.
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Zhang M, Liu W, Huang Q, Han M, Xiang F, Yang Z, Liu J, Wang K. Optical element to generate zero-order quasi-Bessel beam with "focal length". OPTICS LETTERS 2022; 47:553-556. [PMID: 35103669 DOI: 10.1364/ol.448852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Accepted: 12/20/2021] [Indexed: 06/14/2023]
Abstract
An optical element has been invented to generate a zero-order quasi-Bessel beam with a certain distance to the element, which does not exist in the zero-order quasi-Bessel beam by using a traditional axicon. The cross section of designed element is an isosceles triangle whose equal sides are circumscribed by two semi-ellipses. Using a well-developed three-dimensional (3D)-printing technique, we have fabricated a series of elements working at terahertz (THz) frequency. Both simulated and experimental results clearly show that there is a certain distance between the generated quasi-Bessel beam and this element. A physical analysis based on geometric optics theory is performed to explain the obtained results. Because it is a refractive transmitted optical element, we propose that it can be also realized at another frequency band if the relevant processing techniques are available.
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14
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Shi H, Wang K, Yang Z, Liu J. Line imaging of a terahertz zero-order Mathieu-Gauss beam. APPLIED OPTICS 2021; 60:9736-9740. [PMID: 34807158 DOI: 10.1364/ao.438615] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 09/29/2021] [Indexed: 06/13/2023]
Abstract
Thestudy of terahertz (THz) structured beams has become an interesting subject. Here, we use 3D printed diffractive plates to generate a THz zero-order Mathieu-Gauss beam at a frequency of 0.1 THz and simulate its line-imaging effect. According to the nondiffraction property of the beam, we conduct a transmission imaging test by placing the imaging plate at different positions along the direction of beam propagation. The results show that the THz zero-order Mathieu-Gauss beam has a good imaging effect in the depth of field of about 130-380 mm. This can be used in large depth of field THz line imaging.
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15
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Rohrbach D, Kang BJ, Feurer T. 3D-printed THz wave- and phaseplates. OPTICS EXPRESS 2021; 29:27160-27170. [PMID: 34615137 DOI: 10.1364/oe.433881] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 08/02/2021] [Indexed: 06/13/2023]
Abstract
Three-dimensional printing based on fused deposition modeling has been shown to provide a cost-efficient and time-saving tool for fabricating a variety of THz optics for a frequency range of <0.2 THz. By using a broadband THz source, with a useful spectral range from 0.08 THz to 1.5 THz, we show that 3D-printed waveplates operate well up to 0.6 THz and have bandwidths similar to commercial products. Specifically, we investigate quarter- and half-waveplates, q-plates, and spiral phaseplates. We demonstrate a route to achieve broadband performance, so that 3D-printed waveplates can also be used with broadband, few-cycle THz pulses, for instance, in nonlinear THz spectroscopy or other THz high field applications.
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16
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Caustics of Non-Paraxial Perfect Optical Vortices Generated by Toroidal Vortex Lenses. PHOTONICS 2021. [DOI: 10.3390/photonics8070259] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In this paper, we consider the comparative formation of perfect optical vortices in the non-paraxial mode using various optical elements: non-paraxial and parabolic toroidal vortex lenses, as well as a vortex axicon in combination with a parabolic lens. The theoretical analysis of the action of these optical elements, as well as the calculation of caustic surfaces, is carried out using a hybrid geometrical-optical and wave approach. Numerical analysis performed on the basis of the expansion in conical waves qualitatively confirms the results obtained and makes it possible to reveal more details associated with diffraction effects. Equations of 3D-caustic surfaces are obtained and the conditions of the ring radius dependence on the order of the vortex phase singularity are analyzed. In the non-paraxial mode, when small light rings (several tens of wavelengths) are formed, a linear dependence of the ring radius on the vortex order is shown. The revealed features should be taken into account when using the considered optical elements forming the POV in various applications.
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He X, Yang Y, Deng L, Li S, Feng B. 3D Printed Sub-Terahertz All-Dielectric Lens for Arbitrary Manipulation of Quasi-Nondiffractive Orbital Angular Momentum Waves. ACS APPLIED MATERIALS & INTERFACES 2021; 13:20770-20778. [PMID: 33886275 DOI: 10.1021/acsami.1c01443] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Terahertz (THz) vortex waves carrying orbital angular momentum (OAM) hold great potential in dealing with the capacity crunch in wireless high-speed communication systems. Nevertheless, it is quite a challenge for the widespread applications of OAM in the THz regime due to the beam divergence and stringent alignment requirement. To address this issue, an all-dielectric lens (ADL) is proposed for the arbitrary manipulation of quasi-nondiffractive THz OAM waves (QTOWs). On the basis of the concept of the optical conical lens and the multivorticity metasurface, the beam number, the topological charge (TC), and the deflection angle as well as the nondiffractive depth of the generated THz OAM waves are controllable. For proof-of-concept, two ADLs are 3D printed to create single and dual deflected QTOWs, respectively. Remarkably, measured by a THz imaging camera, the desired QTOWs with high mode purity are observed in predesigned directions with a nondiffractive depth predefined theoretically. The proposed designs and experiments, for the first time, verified that the QTOWs could be achieved with a nondiffractive range of 55.58λg (λg = wavelength at 140 GHz) and large deflection angles of 30° and 45°.
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Affiliation(s)
- Xiaoyuan He
- Beijing Laboratory of Advanced Information Networks and Beijing Key Laboratory of Network System Architecture and Convergence, Beijing University of Posts and Telecommunications, Beijing 100089, China
| | - Yang Yang
- Tech Lab, School of Electrical and Data Engineering, University of Technology Sydney, Botany, New South Wales 2019, Australia
| | - Li Deng
- Beijing Laboratory of Advanced Information Networks and Beijing Key Laboratory of Network System Architecture and Convergence, Beijing University of Posts and Telecommunications, Beijing 100089, China
| | - Shufang Li
- Beijing Laboratory of Advanced Information Networks and Beijing Key Laboratory of Network System Architecture and Convergence, Beijing University of Posts and Telecommunications, Beijing 100089, China
| | - Botao Feng
- College of Electronics and Information Engineering, Shenzhen University, Shenzhen, Guangdong 518060, China
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18
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Huang Q, Liu W, Yang Y, Xiao L, Yang Z, Liu J, Wang K. Structuring a terahertz beam by using a 3D-printed n-faced pyramid lens. OPTICS EXPRESS 2021; 29:12124-12130. [PMID: 33984978 DOI: 10.1364/oe.421061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 03/28/2021] [Indexed: 06/12/2023]
Abstract
Using 3D-printed n-faced pyramid lenses, we generate a series of structured diffraction free terahertz (THz) beams. Based on angular spectrum theory, analytical solutions of the output THz beams from these lenses can be obtained. Furthermore, we experimentally realize these non-diffraction THz beams, showing that the measured results are consistent with theory. It is believed that our structured non-diffraction THz beams can be used in THz imaging with large depth of focus.
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19
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Low cost and long-focal-depth metallic axicon for terahertz frequencies based on parallel-plate-waveguides. Sci Rep 2021; 11:3005. [PMID: 33542299 PMCID: PMC7862276 DOI: 10.1038/s41598-021-82503-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Accepted: 01/18/2021] [Indexed: 11/09/2022] Open
Abstract
In this work we demonstrate a triangular surface lens (axicon) operating at frequencies between 350 and 450 GHz using parallel-plate-waveguide technology. The proposed axicon offers longer focal depth characteristics compared to conventional plastic lenses, surpassing common TPX lenses by one order of magnitude. Additionally, due to the triangular surface of the axicon, this device is able to focus THz radiation onto smaller areas than TPX lenses, enhancing the resolution characteristics of THz imaging systems. The frequency range of operation of the proposed axicon can be easily tuned by changing the space between plates, making this approach a very attractive candidate for low-cost, robust and easy to assemble solutions for the next generation of active THz devices.
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20
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“Perfect” Terahertz Vortex Beams Formed Using Diffractive Axicons and Prospects for Excitation of Vortex Surface Plasmon Polaritons. APPLIED SCIENCES-BASEL 2021. [DOI: 10.3390/app11020717] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Transformation of a Bessel beam by a lens results in the formation of a “perfect” vortex beam (PVB) in the focal plane of the lens. The PVB has a single-ring cross-section and carries an orbital angular momentum (OAM) equal to the OAM of the “parent” beam. PVBs have numerous applications based on the assumption of their ideal ring-type structure. For instance, we proposed using terahertz PVBs to excite vortex surface plasmon polaritons propagating along cylindrical conductors and the creation of plasmon multiplex communication lines in the future (Comput. Opt. 2019, 43, 992). Recently, we demonstrated the formation of PVBs in the terahertz range using a Bessel beam produced using a spiral binary silicon axicon (Phys. Rev. A 2017, 96, 023846). It was shown that, in that case, the PVB was not annular, but was split into nested spiral segments, which was obviously a consequence of the method of Bessel beam generation. The search for methods of producing perfect beams with characteristics approaching theoretically possible ones is a topical task. Since for the terahertz range, there are no devices like spatial modulators of light in the visible range, the main method for controlling the mode composition of beams is the use of diffractive optical elements. In this work, we investigated the characteristics of perfect beams, the parent beams being quasi-Bessel beams created by three types of diffractive phase axicons made of high-resistivity silicon: binary, kinoform, and “holographic”. The amplitude-phase distributions of the field in real perfect beams were calculated numerically in the approximation of the scalar diffraction theory. An analytical expression was obtained for the case of the binary axicon. It was shown that a distribution closest to an ideal vortex was obtained using a holographic axicon. The resulting distributions were compared with experimental and theoretical distributions of the evanescent field of a plasmon near the gold–zinc sulfide–air surface at different thicknesses of the dielectric layer, and recommendations for experiments were given.
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21
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Yan B, Wang Z, Zhao X, Lin L, Wang X, Gong C, Liu W. Printing special surface components for THz 2D and 3D imaging. Sci Rep 2020; 10:20867. [PMID: 33257752 PMCID: PMC7705669 DOI: 10.1038/s41598-020-77998-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2020] [Accepted: 11/10/2020] [Indexed: 11/17/2022] Open
Abstract
The paper reports an off-axis large focal depth THz imaging system which consists of three 3D printed special surface components (two aspherical mirrors and an axicon). Firstly, the optical design software is used to design and optimize the aspherical parabolic mirror. Secondly, the optimized mirror is prepared by a 3D printing and metal cladding method. Thirdly, a THz axicon is designed for generation of quasi-Bessel Beam and a new geometric theoretical model of oblique incident light for axicon is established. Finally, the imaging system based on the special surface components is constructed. Its maximum diffraction-free distance is about 60 mm, which is 6 times higher than the traditional system. To verify the effectiveness, THz two-dimensional imaging experiments and three-dimensional computed tomography experiment are carried out. The results are consistent with the design and calculations.
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Affiliation(s)
- Bo Yan
- School of Electronic Engineering, University of Electronic Science and Technology, Chengdu, 611731, China
| | - Zhigang Wang
- School of Electronic Engineering, University of Electronic Science and Technology, Chengdu, 611731, China
| | - Xing Zhao
- Institute of Modern Optics, Tianjin Key Laboratory of Micro-Scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| | - Lie Lin
- Institute of Modern Optics, Tianjin Key Laboratory of Micro-Scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| | - Xiaolei Wang
- Institute of Modern Optics, Tianjin Key Laboratory of Micro-Scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| | - Cheng Gong
- Institute of Modern Optics, Tianjin Key Laboratory of Micro-Scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China.
| | - Weiwei Liu
- Institute of Modern Optics, Tianjin Key Laboratory of Micro-Scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
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22
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Xiang F, Liu D, Xiao L, Shen S, Yang Z, Liu J, Wang K. Generation of a meter-scale THz diffraction-free beam based on multiple cascaded lens-axicon doublets: detailed analysis and experimental demonstration. OPTICS EXPRESS 2020; 28:36873-36883. [PMID: 33379771 DOI: 10.1364/oe.408692] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 11/11/2020] [Indexed: 06/12/2023]
Abstract
An effective approach is proposed for obtaining a long-distance THz diffraction-free beam with meter-scale length. Multiple 3D-printed lens-axicon doublets are cascaded to form the generation system. In order to manifest the physical mechanism behind the generation process of this long-distance diffraction-free beam, we make a detailed comparative analysis of three beams: the ideal Bessel beam, the quasi-Bessel beam generated by single axicon, and the diffraction-free beam generated by the lens-axicon doublets. Theoretical results show that the zero-radial-spatial-frequency component plays a key role during the generation process of the third beam. Moreover, the intensities of this component are enhanced with the increase in the number of lens-axicon doublets, making the diffraction-free length longer. An experiment containing three lens-axicon doublets is performed to demonstrate the feasibility of our design. A 0.1-THz beam with one-meter diffraction-free length was successfully generated. Further experiments indicate that this THz diffraction-free beam also has a self-healing property. We believe that such long-distance diffraction-free beams can be used in practical THz remote sensing or imaging.
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23
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He H, Kong C, Chan KY, So WL, Fok HK, Ren YX, Lai CSW, Tsia KK, Wong KKY. Resolution enhancement in an extended depth of field for volumetric two-photon microscopy. OPTICS LETTERS 2020; 45:3054-3057. [PMID: 32479457 DOI: 10.1364/ol.394282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Accepted: 05/05/2020] [Indexed: 06/11/2023]
Abstract
The resolution enhancement over the extended depth of field (DOF) in the volumetric two-photon microscopy (TPM) is demonstrated by utilizing multiple orders of Bessel beams. Here the conventional method of switching laser modes (SLAM) in 2D is introduced to 3D, denoted as the volumetric SLAM (V-SLAM). The equivalent scanning beam in the TPM is a thin needle-like beam, which is generated from the subtraction between the needle-like 0th-order and the straw-like 1st-order Bessel beams. Compared with the 0th-order Bessel beam, the lateral resolution of the V-SLAM is increased by 28.6% and maintains over the axial depth of 56 µm. The V-SLAM performance is evaluated by employing fluorescent beads and a mouse brain slice. The V-SLAM approach provides a promising solution to improve the lateral resolutions for fast volumetric imaging on sparsely distributed samples.
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Yang Y, Niu L, Yang Z, Liu J. Measuring the topological charge of terahertz vortex beams with a focal hyperbolic lens. APPLIED OPTICS 2020; 59:4685-4691. [PMID: 32543577 DOI: 10.1364/ao.388111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 04/06/2020] [Indexed: 06/11/2023]
Abstract
An efficient method is proposed to measure the topological charge (TC) of terahertz (THz) vortex beams with a focal hyperbolic (FH) lens at 0.1 THz. The FH lens is designed and fabricated by 3D printing. The diffraction fringes acquired in the focal plane of the FH lens can judge the number and sign of the TC. Furthermore, after the horizontal or vertical measurement curve is recorded by rotating the FH lens to a suitable angle, the TC value can then be simply and effectively identified. The TC value of the experiment measurement reaches 5. The experiment results are in excellent accord with the simulation.
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25
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Yang Y, Ye X, Niu L, Wang K, Yang Z, Liu J. Generating terahertz perfect optical vortex beams by diffractive elements. OPTICS EXPRESS 2020; 28:1417-1425. [PMID: 32121853 DOI: 10.1364/oe.380076] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2019] [Accepted: 12/22/2019] [Indexed: 06/10/2023]
Abstract
An effective experiment scheme is proposed to generate the terahertz (THz) perfect optical vortex (POV) beams by diffractive elements at the frequency of 0.1THz. Two diffractive elements are designed and fabricated by 3D-printing to form the generation system. The ring radius of the generated beams is independent of the topological charge and positive linear relationship with the radial wave vector. By controlling the radial wave vector, the ring radius can be freely adjusted. The experiment results are shown to corroborate the numerical simulation ones. Such generated beams hold promise for developing the novel THz fiber communication systems.
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26
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Fortin M, Piché M, Brousseau D, Thibault S. Generation of optical Y-junction Bessel beams. APPLIED OPTICS 2019; 58:8411-8415. [PMID: 31873323 DOI: 10.1364/ao.58.008411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Accepted: 09/29/2019] [Indexed: 06/10/2023]
Abstract
A method is proposed to split the central spot of zero-order Bessel beams into two parallel spots along the propagation axis of the beam. A magnetic-liquid deformable mirror is used to provide the required phase profile combining an axicon and a phase step. The obtained Y-junction Bessel beam has been characterized; the 80 µm central spot of the Bessel beam is split into two spots of the same size that have been propagated over a length exceeding 15 cm. The observations are consistent with the predictions of a numerical model. Potential applications of Y-junction Bessel beams are discussed.
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27
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Kulya M, Semenova V, Gorodetsky A, Bespalov VG, Petrov NV. Spatio-temporal and spatiospectral metrology of terahertz broadband uniformly topologically charged vortex beams. APPLIED OPTICS 2019; 58:A90-A100. [PMID: 30873965 DOI: 10.1364/ao.58.000a90] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Accepted: 11/10/2018] [Indexed: 06/09/2023]
Abstract
A comprehensive characterization of the diffraction properties of terahertz (THz) pulsed broadband vortex beams consisting of several electromagnetic field oscillations requires state-of-the-art techniques for studying the evolution of a wavefront as it propagates. For this purpose, we have applied the capabilities offered by THz pulse time domain holography. Accurate metrological study of pulsed single-period THz field propagation allowed us to reveal the spatio-temporal and spatiospectral couplings in broadband uniformly topologically charged vortex beams. Here, we reveal dynamics of such beam propagation in a free space as well as in the experiment with edge diffraction with 50% blocking of the beam focal waist. In this study, we compare the dynamics of freely propagating and edge-diffracted THz vortex. Despite the fact that in the amplitude representation one can observe the emergence of strong asymmetry, analysis of the spectral trajectory of the singular point at some distance from the obstacle and the visualization of phase distribution for individual spectral components testify to the conservation of transverse energy circulation. Similar to the edge diffraction of monochromatic optical vortices, it can be interpreted as self-reconstruction of vortex properties. The given term has not previously been used for the case of pulsed broadband THz beams, to the best of our knowledge.
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28
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Dong XP, Cheng JR, Fan F, Xu ST, Wang XH, Chang SJ. Wideband sub-THz half-wave plate using 3D-printed low-index metagratings with superwavelength lattice. OPTICS EXPRESS 2019; 27:202-211. [PMID: 30645368 DOI: 10.1364/oe.27.000202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 12/20/2018] [Indexed: 06/09/2023]
Abstract
High-index dielectric metasurfaces are rarely reported around 0.1-0.3 THz, as an extremely large etching depth is needed according to the millimeter-scale wavelength. In this work, we propose an easy solution to sub-THz wideband polarization control by utilizing 3D-printed low-index (n~1.5) metagratings. The metagrating with subwavelength lattice is shown as a very efficient half-wave plate (net polarization conversion of 87%) at 0.14 THz but showing noisy spectrum. The design with superwavelength lattice offers a smooth and wide bandwidth for linear polarization rotation. Study of the mechanism shows that the lattice size slightly above wavelength is a better choice for the low-index metadevice as it maintains high efficiency in the zero diffraction order and wide bandwidth due to the small mode dispersion. Such designs offer a feasible solution especially suitable for sub-THz polarization and phase control, complementary to the existing high-index dielectric and metallic metasurfaces.
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29
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Wu Z, Han Y, Wang J, Cui Z. Generation of Bessel beam sources in FDTD. OPTICS EXPRESS 2018; 26:28727-28737. [PMID: 30470045 DOI: 10.1364/oe.26.028727] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Accepted: 10/14/2018] [Indexed: 06/09/2023]
Abstract
In this paper, a straightforward approach is presented to generate Bessel beam sources in three-dimensional finite-difference time-domain (FDTD) method. Based on the angular spectrum representation (ASR), the incident Bessel beam is described as a superposition of plane waves whose wavevectors covering a conical surface. This decomposition of Bessel beam is then approximated by a finite collection of plane waves, which are injected into FDTD simulation domain using the total-field/scattered-field (TF/ST) method. The present method's correctness and accuracy are verified by comparing the reconstructed field in FDTD with the original field. Far-field scattered diagrams of a dielectric sphere and a spheroid particle illuminated by a zero-order or a higher-order Bessel beam are calculated using FDTD. The results are compared with those calculated using the generalized Lorenz-Mie theory (GLMT) and surface integral equation method (SIEM). Very good agreements have been achieved, which partially indicate the correctness of our method. Internal and near-surface field distributions for a two-layer hemisphere particle, which are illuminated by Bessel beams, are also displayed to show the potentials of this approach in solving scattering problems of complex particles. This approach can also be applied to generate other structured beam sources in FDTD, which provides an access to solve structured beam scattering by complex particles using FDTD.
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30
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Fortin M, Piché M, Brousseau D, Thibault S. Generation of optical Bessel beams with arbitrarily curved trajectories using a magnetic-liquid deformable mirror. APPLIED OPTICS 2018; 57:6135-6144. [PMID: 30117994 DOI: 10.1364/ao.57.006135] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Accepted: 06/20/2018] [Indexed: 06/08/2023]
Abstract
We propose a new strategy to curve the trajectory of the central lobe of a zero-order Bessel beam and a first-order Bessel beam along their propagation axis. Our method involves modifying the phase of a beam that is incident on an adaptive mirror. As examples, we show that the most intense lobe of the beam can follow a parabolic trajectory, a cubic trajectory, or a trajectory made by a combination of these orders. By using a phase correction emulating the effect of cylindrical mirrors, the central lobe always preserves its symmetry. Theoretical simulations were reproduced in the laboratory using a magnetic-liquid deformable mirror. The parabolic trajectory of the 60-μm central spot of a zero-order Bessel beam exhibits a 0.6-mm off-axis shift after 30-cm-length propagation.
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31
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Wu Z, Wang X, Sun W, Feng S, Han P, Ye J, Yu Y, Zhang Y. Vectorial diffraction properties of THz vortex Bessel beams. OPTICS EXPRESS 2018; 26:1506-1520. [PMID: 29402024 DOI: 10.1364/oe.26.001506] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 01/09/2018] [Indexed: 06/07/2023]
Abstract
A vortex Bessel beam combines the merits of an optical vortex and a Bessel beam, including a spiral wave front and a non-diffractive feature, which has immense application potentials in optical trapping, optical fabrication, optical communications, and so on. Here, linearly and circularly polarized vortex Bessel beams in the terahertz (THz) frequency range are generated by utilizing a THz quarter wave plate, a spiral phase plate, and Teflon axicons with different opening angles. Taking advantage of a THz focal-plane imaging system, vectorial diffraction properties of the THz vortex Bessel beams are comprehensively characterized and discussed, including the transverse (Ex, Ey) and longitudinal (Ez) polarization components. The experimental phenomena are accurately simulated by adopting the vectorial Rayleigh diffraction integral. By varying the opening angle of the axicon, the characteristic parameters of these THz vortex Bessel beams are exhibited and compared, including the light spot size, the diffraction-free range, and the phase evolution process. This work provides the precise experimental and theoretical bases for the comprehension and application of a THz vortex Bessel beam.
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32
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Lightman S, Hurvitz G, Gvishi R, Arie A. Tailoring lens functionality by 3D laser printing. APPLIED OPTICS 2017; 56:9038-9043. [PMID: 29131190 DOI: 10.1364/ao.56.009038] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 10/13/2017] [Indexed: 06/07/2023]
Abstract
Conversion of a Gaussian beam into a top-hat beam or to an annular beam is demonstrated using 3D direct laser printing. Micron-scale refractive phase elements were designed and printed directly on standard commercially available lenses. These structures modify the phase of the incoming beam into either three intensity-flattened profiles, having line, square, or circular shapes, or to an annular beam profile. This method to functionalize lenses opens new and exciting opportunities for compact and robust beam shaping, as well as for reduction of the aberrations of the lens itself.
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33
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Wu Z, Wang X, Sun W, Feng S, Han P, Ye J, Zhang Y. Vector characterization of zero-order terahertz Bessel beams with linear and circular polarizations. Sci Rep 2017; 7:13929. [PMID: 29066716 PMCID: PMC5655669 DOI: 10.1038/s41598-017-12524-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 09/11/2017] [Indexed: 12/02/2022] Open
Abstract
As a kind of special beams, Bessel beams are always a research hot spot in optics due to its non-diffractive and self-healing properties. Here, zero-order terahertz (THz) Bessel beams with linear and circular polarizations are generated by using a THz quarter wave plate and Teflon axicons with different opening angles. By applying a THz digital holographic imaging system, the evolutions of the transverse (Ex, Ey) and longitudinal (Ez) electric fields are coherently measured and analyzed during the propagation processes of the THz Bessel beams. The vectorial Rayleigh diffraction integral is used to accurately reproduce the amplitude, phase, and non-diffractive feature of each polarization component for the THz Bessel beams. With varying opening angles of the axicons, the focal spots, diffraction-free ranges, and Gouy phase shifts of the THz Bessel beams are compared and discussed. The experiment and simulation results provide a comprehensive view for exactly understanding peculiar features of THz Bessel beams.
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Affiliation(s)
- Zhen Wu
- Beijing Key Laboratory of Metamaterials and Devices, Beijing Advanced Innovation Center for Imaging Technology, Key Laboratory of Terahertz Optoelectronics, Ministry of Education, and Department of Physics, Capital Normal University, Beijing, 100048, P.R. China
| | - Xinke Wang
- Beijing Key Laboratory of Metamaterials and Devices, Beijing Advanced Innovation Center for Imaging Technology, Key Laboratory of Terahertz Optoelectronics, Ministry of Education, and Department of Physics, Capital Normal University, Beijing, 100048, P.R. China.
| | - Wenfeng Sun
- Beijing Key Laboratory of Metamaterials and Devices, Beijing Advanced Innovation Center for Imaging Technology, Key Laboratory of Terahertz Optoelectronics, Ministry of Education, and Department of Physics, Capital Normal University, Beijing, 100048, P.R. China
| | - Shengfei Feng
- Beijing Key Laboratory of Metamaterials and Devices, Beijing Advanced Innovation Center for Imaging Technology, Key Laboratory of Terahertz Optoelectronics, Ministry of Education, and Department of Physics, Capital Normal University, Beijing, 100048, P.R. China
| | - Peng Han
- Beijing Key Laboratory of Metamaterials and Devices, Beijing Advanced Innovation Center for Imaging Technology, Key Laboratory of Terahertz Optoelectronics, Ministry of Education, and Department of Physics, Capital Normal University, Beijing, 100048, P.R. China
| | - Jiasheng Ye
- Beijing Key Laboratory of Metamaterials and Devices, Beijing Advanced Innovation Center for Imaging Technology, Key Laboratory of Terahertz Optoelectronics, Ministry of Education, and Department of Physics, Capital Normal University, Beijing, 100048, P.R. China
| | - Yan Zhang
- Beijing Key Laboratory of Metamaterials and Devices, Beijing Advanced Innovation Center for Imaging Technology, Key Laboratory of Terahertz Optoelectronics, Ministry of Education, and Department of Physics, Capital Normal University, Beijing, 100048, P.R. China
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Abstract
Vortex beams have received considerable research interests both in optical and millimeter-wave domain since its potential to be utilized in the wireless communications and novel imaging systems. Many well-known optical beams have been demonstrated to carry orbital angular momentum (OAM), such as Laguerre-Gaussian beams and high-order Bessel beams. Recently, the radially symmetric Airy beams that exhibit an abruptly autofocusing feature are also demonstrated to be capable of carrying OAM in the optical domain. However, due to the lack of efficient devices to manipulate terahertz (THz) beams, it could be a challenge to demonstrate the radially symmetric Airy beams in the THz domain. Here we demonstrate the THz circular Airy vortex beams (CAVBs) with a 0.3-THz continuous wave through 3D printing technology. Assisted by the rapidly 3D-printed phase plates, individual OAM states with topological charge l ranging from l = 0 to l = 3 and a multiplexed OAM state are successfully imposed into the radially symmetric Airy beams. We both numerically and experimentally investigate the propagation dynamics of the generated THz CAVBs, and the simulations agree well with the observations.
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35
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Di Domenico G, Parravicini J, Antonacci G, Silvestri S, Agranat AJ, DelRe E. Miniaturized photogenerated electro-optic axicon lens Gaussian-to-Bessel beam conversion. APPLIED OPTICS 2017; 56:2908-2911. [PMID: 28375260 DOI: 10.1364/ao.56.002908] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We experimentally demonstrate an electro-optic Gaussian-to-Bessel beam-converter miniaturized down to a 30×30 μm pixel in a potassium-lithium-tantalate-niobate (KLTN) paraelectric crystal. The converter is based on the electro-optic activation of a photoinduced and reconfigurable volume axicon lens achieved using a prewritten photorefractive funnel space-charge distribution. The transmitted light beam has a tunable depth of field that can be more than twice that of a conventional beam with the added feature of being self-healing.
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36
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Minasyan A, Trovato C, Degert J, Freysz E, Brasselet E, Abraham E. Geometric phase shaping of terahertz vortex beams. OPTICS LETTERS 2017; 42:41-44. [PMID: 28059173 DOI: 10.1364/ol.42.000041] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We propose a topological beam-shaping strategy of terahertz (THz) beams using geometric phase elements made of space-variant birefringent slabs. Quasi-monochromatic THz vortex beams are produced and characterized both in amplitude and phase from the reconstructed real-time two-dimensional imaging of the electric field. Nonseparable superpositions of such vortex beams are also obtained and characterized by two-dimensional polarimetric analysis. These results emphasize the versatility of the spin-orbit electromagnetic toolbox to prepare on-demand structured light endowed with polarization-controlled orbital angular momentum content in the THz domain, which should find many uses in future THz technologies.
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37
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Knyazev B, Cherkassky V, Choporova Y, Kameshkov O, Kulipanov G, Osintseva N, Pavelyev V, Vinokurov N, Volodkin B. Wave beams with orbital angular momentum: a step towards terahertz. EPJ WEB OF CONFERENCES 2017. [DOI: 10.1051/epjconf/201714905001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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38
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Choporova Y, Knyazev B, Osintseva N, Pavelyev V, Volodkin B. Terahertz Bessel beams with orbital angular momentum: diffraction and interference. EPJ WEB OF CONFERENCES 2017. [DOI: 10.1051/epjconf/201714905003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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39
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Miyamoto K, Kang BJ, Kim WT, Sasaki Y, Niinomi H, Suizu K, Rotermund F, Omatsu T. Highly intense monocycle terahertz vortex generation by utilizing a Tsurupica spiral phase plate. Sci Rep 2016; 6:38880. [PMID: 27966595 PMCID: PMC5155293 DOI: 10.1038/srep38880] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 11/15/2016] [Indexed: 11/28/2022] Open
Abstract
Optical vortex, possessing an annular intensity profile and an orbital angular momentum (characterized by an integer termed a topological charge) associated with a helical wavefront, has attracted great attention for diverse applications due to its unique properties. In particular for terahertz (THz) frequency range, several approaches for THz vortex generation, including molded phase plates consisting of metal slit antennas, achromatic polarization elements and binary-diffractive optical elements, have been recently proposed, however, they are typically designed for a specific frequency. Here, we demonstrate highly intense broadband monocycle vortex generation near 0.6 THz by utilizing a polymeric Tsurupica spiral phase plate in combination with tilted-pulse-front optical rectification in a prism-cut LiNbO3 crystal. A maximum peak power of 2.3 MW was obtained for THz vortex output with an expected topological charge of 1.15. Furthermore, we applied the highly intense THz vortex beam for studying unique nonlinear behaviors in bilayer graphene towards the development of nonlinear super-resolution THz microscopy and imaging system.
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Affiliation(s)
- Katsuhiko Miyamoto
- Graduate School of Advanced Integration Science, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.,Molecular Chirality Research Center, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Bong Joo Kang
- Department of Physics and Department of Energy Systems Research, Ajou University, 206 Worldcup-ro, Yeongtong-gu, Suwon 16499, Korea
| | - Won Tae Kim
- Department of Physics and Department of Energy Systems Research, Ajou University, 206 Worldcup-ro, Yeongtong-gu, Suwon 16499, Korea
| | - Yuta Sasaki
- Graduate School of Advanced Integration Science, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Hiromasa Niinomi
- Graduate School of Advanced Integration Science, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.,Molecular Chirality Research Center, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Koji Suizu
- Department of Electrical, Electronics and Computer Engineering, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan
| | - Fabian Rotermund
- Department of Physics and Department of Energy Systems Research, Ajou University, 206 Worldcup-ro, Yeongtong-gu, Suwon 16499, Korea.,Department of Physics, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Korea
| | - Takashige Omatsu
- Graduate School of Advanced Integration Science, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.,Molecular Chirality Research Center, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
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Generation of radially-polarized terahertz pulses for coupling into coaxial waveguides. Sci Rep 2016; 6:38926. [PMID: 27941845 PMCID: PMC5150854 DOI: 10.1038/srep38926] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 11/15/2016] [Indexed: 11/24/2022] Open
Abstract
Coaxial waveguides exhibit no dispersion and therefore can serve as an ideal channel for transmission of broadband THz pulses. Implementation of THz coaxial waveguide systems however requires THz beams with radially-polarized distribution. We demonstrate the launching of THz pulses into coaxial waveguides using the effect of THz pulse generation at semiconductor surfaces. We find that the radial transient photo-currents produced upon optical excitation of the surface at normal incidence radiate a THz pulse with the field distribution matching the mode of the coaxial waveguide. In this simple scheme, the optical excitation beam diameter controls the spatial profile of the generated radially-polarized THz pulse and allows us to achieve efficient coupling into the TEM waveguide mode in a hollow coaxial THz waveguide. The TEM quasi-single mode THz waveguide excitation and non-dispersive propagation of a short THz pulse is verified experimentally by time-resolved near-field mapping of the THz field at the waveguide output.
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Liu C, Niu L, Wang K, Liu J. 3D-printed diffractive elements induced accelerating terahertz Airy beam. OPTICS EXPRESS 2016; 24:29342-29348. [PMID: 27958594 DOI: 10.1364/oe.24.029342] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We first demonstrate the accelerating terahertz (THz) Airy beam with a 0.3-THz continuous wave. Two diffractive elements are designed and 3D-printed to form the generation system, which cannot only imprint the desired complex phase pattern but also perform the required Fourier transform (FT). We both numerically and experimentally demonstrate the propagation dynamics of the accelerating THz Airy beam and investigate its self-healing property during propagation in the free space. Our observations are in good agreement with the numerical simulations. Such an accelerating THz Airy beam could be able to develop novel THz imaging systems and robust THz communication links.
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Liu C, Wei X, Niu L, Wang K, Yang Z, Liu J. Discrimination of orbital angular momentum modes of the terahertz vortex beam using a diffractive mode transformer. OPTICS EXPRESS 2016; 24:12534-41. [PMID: 27410274 DOI: 10.1364/oe.24.012534] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
We present an efficient method to discriminate orbital angular momentum (OAM) of the terahertz (THz) vortex beam using a diffractive mode transformer. The mode transformer performs a log-polar coordinate transformation of the input THz vortex beam, which consists of two 3D-printed diffractive elements. A following lens separates each transformed OAM mode to a different lateral position in its focal plane. This method enables a simultaneous measurement over multiple OAM modes of the THz vortex beam. We experimentally demonstrate the measurement of seven individual OAM modes and two multiplexed OAM modes, which is in good agreement with simulations.
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