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Photonics
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Vortex Beams: Fundamentals and Applications
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Vortex Beams: Fundamentals and Applications

A special issue of Photonics (ISSN 2304-6732).

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 35003

Special Issue Editors

Prof. Dr. Yangjian Cai

E-Mail Website
Guest Editor
1. School of Physics and Electronics, Shandong Normal University, Jinan 250014, China
2. School of Physical Science and Technology, Soochow University, Suzhou 215006, China
Interests: light manipulations and applications; optical vortex beams; optical coherence and polarization; turbulent atmosphere; optical imaging
Prof. Dr. Yuanjie Yang

E-Mail Website
Guest Editor
School of Physics, University of Electronic Science and Technology of China, Chengdu 611731, China
Interests: optical vortex beams; plasmonic vortices; optical tweezers; light manipulations; free space optics

Special Issue Information

Dear Colleagues,

It is well known that vortices are inherent to any wave phenomena, and in general, vortex beams denote optical vortex beam. The vortex beams have become one of the most important light sources today, due to each photon of vortex beams can carry ℓħ orbital angular momentum (OAM), where ℓ known as the topological charge and ħ denoting the reduced Plank constant. Thus far, vortex beams have found a wide variety of applications, for example, classical optical communications and quantum communications, optical manipulation, optical metrology  and imaging, to mention but a few. Besides optical vortex beams, some other vortices, such as  electron vortex beams, neutron atom vortex beams, plasmonic vortices and radio vortices, can carry OAM as well, and may lead to a new wide-range of applications in many fields.

Over the past three decades, significant fundamental studies on vortex beams have been carried out, from paraxial model to non-paraxial model, from scalar beams to vectorial beams. Dynamical characteristics of polarization singularities, coherence singularities, and speckle fields have been extensively studied as well. Meanwhile, different approaches and technologies have been proposed to generate vortex beams and measuring its OAM.  Consequently, with the advance of optical vortex beams, the rapid development of optical technologies, such as optical manipulation, optically driven motors, data processing, imaging, optical sorting, delivering, etc., have been achieved.

This Special Issue aims at presenting state-of-the-art articles on both the theoretical and experimental studies on generation, propagation and measurement of vortex beams, and applications of vortex beams. Topics include, but are not limited to:

  • Vortex Dynamics
  • Partially coherent vortex beams
  • Fractional vortex beam
  • Plasmonics vortices
  • Vector vortex beams
  • Orbital angular momentum
  • Applications of vortex beams

Prof. Dr. Yangjian Cai
Prof. Dr. Yuanjie Yang
Guest Editors

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Keywords

  • Vortex beam
  • Fractional vortex beam
  • Vector vortex beam
  • Vortex Dynamics
  • Plasmonics vortices
  • Coherence
  • Polarization
  • Orbital angular momentum
  • Applications

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Published Papers (14 papers)

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Research

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9 pages, 2983 KiB  
Communication
Generation of Vector Vortex Beams Based on the Optical Integration of Dynamic Phase and Geometric Phase
by Kuiming Zeng, Shanshan He, Xianping Wang and Hailu Luo
Photonics 2023, 10(2), 214; https://doi.org/10.3390/photonics10020214 - 15 Feb 2023
Cited by 4 | Viewed by 2341
Abstract
The phase and polarization of electromagnetic waves can be conveniently manipulated by the dynamic phase and geometric phase elements. Here, we propose a compact optical integration of dynamic phase and geometric phase to generate arbitrary vector vortex beams on a hybrid-order Poincaré sphere. [...] Read more.
The phase and polarization of electromagnetic waves can be conveniently manipulated by the dynamic phase and geometric phase elements. Here, we propose a compact optical integration of dynamic phase and geometric phase to generate arbitrary vector vortex beams on a hybrid-order Poincaré sphere. Two different technologies have been applied to integrate dynamic and geometric phase elements into a single glass plate to modulate the phase and polarization of light simultaneously. A spiral phase structure is made on one side of a glass substrate with optical lithography and a geometric phase metasurface structure is designed on the other side by femtosecond laser writing. The vector polarization is realized by the metasurface structure, while the vortex phase is generated by the spiral phase plate. Therefore, any desirable vector vortex beams on the hybrid-order Poincaré sphere can be generated. We believe that our scheme may have potential applications in future integrated optical devices for the generation of vector vortex beams due to its the high transmission efficiency and conversion efficiency. Full article
(This article belongs to the Special Issue Vortex Beams: Fundamentals and Applications)
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11 pages, 3055 KiB  
Communication
Holographic Writing of Forked Diffraction Gratings on the Surface of a Chalcogenide Glass Semiconductor
by Nikolay A. Ivliev, Svetlana N. Khonina, Vladimir V. Podlipnov and Sergey V. Karpeev
Photonics 2023, 10(2), 125; https://doi.org/10.3390/photonics10020125 - 27 Jan 2023
Cited by 5 | Viewed by 1888
Abstract
We consider the formation of forked diffraction gratings on the surface of a multilayer structure based on chalcogenide glass semiconductors As2S3 and a-Se is. The distribution of electric field components upon interference of beams with different polarization states is analyzed [...] Read more.
We consider the formation of forked diffraction gratings on the surface of a multilayer structure based on chalcogenide glass semiconductors As2S3 and a-Se is. The distribution of electric field components upon interference of beams with different polarization states is analyzed theoretically. The possibility of direct holographic writing of diffraction gratings with a “forked” structure is demonstrated. The parameters of vortex laser beams generated by the microrelief formed are examined. Full article
(This article belongs to the Special Issue Vortex Beams: Fundamentals and Applications)
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11 pages, 2814 KiB  
Communication
Theoretical Analysis of Continuous-Wave Mid-Infrared Optical Vortex Source Generated by Singly Resonant Optical Parametric Oscillator
by Ziheng Zhou, Shirui Zhang, Yuanhao Duan, Minghao Guo and Peng Li
Photonics 2022, 9(12), 1002; https://doi.org/10.3390/photonics9121002 - 19 Dec 2022
Cited by 1 | Viewed by 1842
Abstract
Due to the important application in the study of vibrational circular dichroism and helical dichroism of chiral molecules, the tunable vortex beam at mid-infrared region has attracted increasing attention. Based on orbital angular momentum (OAM) conservation in nonlinear interactions, the vortex pumped singly [...] Read more.
Due to the important application in the study of vibrational circular dichroism and helical dichroism of chiral molecules, the tunable vortex beam at mid-infrared region has attracted increasing attention. Based on orbital angular momentum (OAM) conservation in nonlinear interactions, the vortex pumped singly resonant optical parametric oscillator (SRO) is recognized as a versatile source of coherent vortex radiation providing high power and broad wavelength coverage from a single device. However, the low parametric gain and high oscillation threshold under continuous wave (cw) pumping has so far been the most challenging factor in generating cw tunable vortex beams. To predict the output characteristic of vortex pumped SRO, a theoretical model describing the vortex pumped SRO is needed. In this study, the theoretical model describing the vortex pumped SRO is set up under collimated Gaussian beam approximation. Output characteristics of different SROs are simulated numerically. By proper selection of pump scheme (such as double-pass pumping scheme), the vortex pumped mid-infrared SRO can oscillate at a relatively low pump power. By controlling the gain (mode overlap ratio between the pump and resonant wave in the nonlinear crystal) and loss (employing a spot-defect mirror with different defect size as the output coupler) of the resonant signal mode in the SRO, the OAM of the pump beam can be directionally transferred to a specific down converted beam. The transfer mechanism of the OAM among the pump light and the down-converted beams and factors affecting the transfer are studied. Our study provides the guidelines for the design and optimization of vortex pumped SRO under cw operation. Full article
(This article belongs to the Special Issue Vortex Beams: Fundamentals and Applications)
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8 pages, 1558 KiB  
Communication
High-Order Orbital and Spin Hall Effects at the Tight Focus of Laser Beams
by Victor V. Kotlyar, Sergey S. Stafeev, Elena S. Kozlova and Muhammad A. Butt
Photonics 2022, 9(12), 970; https://doi.org/10.3390/photonics9120970 - 11 Dec 2022
Cited by 8 | Viewed by 1894
Abstract
In this paper, using a Richards–Wolf method, which describes the behavior of electromagnetic waves at the sharp focus, we show that high-order spin and orbital Hall effects take place at the focal plane of tightly focused laser beams. We reveal that four local [...] Read more.
In this paper, using a Richards–Wolf method, which describes the behavior of electromagnetic waves at the sharp focus, we show that high-order spin and orbital Hall effects take place at the focal plane of tightly focused laser beams. We reveal that four local subwavelength regions are formed at the focus of a linearly polarized optical vortex with unit topological charge, where the spin angular momentum behaves in a special way. Longitudinal projections of the spin angular momentum are oppositely directed in the adjacent regions. We conclude that this is because photons falling into the neighboring regions at the focus have the opposite spin. This newly observed phenomenon may be called a spin Hall effect of the 4-th order. We also show that tightly focusing the superposition of cylindrical vector beams of the m-th and zero-order produces 2m subwavelength regions in the focal plane, such that longitudinal projections of the orbital angular momentum are oppositely directed in the neighboring regions. This occurs because photons falling into the neighboring regions at the focus have the opposite signs of the on-axis projections of the orbital angular momentum. This phenomenon may be termed an orbital Hall effect of the 2m-th order. Full article
(This article belongs to the Special Issue Vortex Beams: Fundamentals and Applications)
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7 pages, 2471 KiB  
Communication
An Orbital-Angular-Momentum- and Wavelength-Tunable 2 μm Vortex Laser
by Xinmiao Zhao, Jingliang Liu, Mingming Liu, Ruobing Li, Luan Zhang and Xinyu Chen
Photonics 2022, 9(12), 926; https://doi.org/10.3390/photonics9120926 - 1 Dec 2022
Cited by 2 | Viewed by 1368
Abstract
In this paper, dual tuning of orbital angular momentum (OAM) and the wavelength of a Tm:YLF vortex laser was realized by off-axis pumping and F-P etalon. The tuning of Hermite–Gaussian (HG) modes by off-axis pumping was theoretically analyzed. In the experiment, the highest [...] Read more.
In this paper, dual tuning of orbital angular momentum (OAM) and the wavelength of a Tm:YLF vortex laser was realized by off-axis pumping and F-P etalon. The tuning of Hermite–Gaussian (HG) modes by off-axis pumping was theoretically analyzed. In the experiment, the highest 17th order HG17,0 mode was realized by off-axis pumping. The threshold power increased from 2 to 17.51 W with the increase in off-axis distance, and the curve of threshold power vs. off-axis distance was partially consistent with the theoretical simulation analysis. The Laguerre–Gaussian (LG) modes carrying OAM were produced by mode converter, and the beam quality of LG modes was good. The phase distribution of the LG modes was verified by interference. Subsequently, an F-P etalon was inserted into the resonant cavity to tune the wavelength. Finally, the OAM tuning of the vortex beam from LG1,0(OAM = −1ℏ) to LG16,0(OAM = −16ℏ) was realized, and the corresponding wavelength tuning range was from 1898–1943 nm to 1898–1937 nm. Full article
(This article belongs to the Special Issue Vortex Beams: Fundamentals and Applications)
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8 pages, 2740 KiB  
Article
Generation of Tunable Plasmonic Vortices by Varying Wavelength of Incident Light
by Yihua Bai, Qing Zhang and Yuanjie Yang
Photonics 2022, 9(11), 809; https://doi.org/10.3390/photonics9110809 - 27 Oct 2022
Cited by 5 | Viewed by 1752
Abstract
Surfaces plasmon polaritons carrying orbital angular momentum (OAM), known as plasmonic vortex, hold potential applications for on-chip information multiplexing. However, a traditional plasmonic vortex lens was usually designed for monochromatic incident light and encountered challenges in generating multiple vortices. Here, we demonstrated a [...] Read more.
Surfaces plasmon polaritons carrying orbital angular momentum (OAM), known as plasmonic vortex, hold potential applications for on-chip information multiplexing. However, a traditional plasmonic vortex lens was usually designed for monochromatic incident light and encountered challenges in generating multiple vortices. Here, we demonstrated a wavelength-tunable plasmonic vortex generator that ameliorates these limits, relying on the simultaneous design of a geometric metasurface on an Archimedean spiral. Through this design strategy, both the topological charges and the location of vortices can be controlled with different wavelengths of incident beams. This design and concept can preserve incident wavelength information and can be further applied to integrated and high-dimensional on-chip devices. Full article
(This article belongs to the Special Issue Vortex Beams: Fundamentals and Applications)
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12 pages, 3961 KiB  
Article
Holographic Tailoring of Structured Light Field with Digital Device
by Zhensong Wan, Zijian Shi, Qiang Liu and Xing Fu
Photonics 2022, 9(7), 506; https://doi.org/10.3390/photonics9070506 - 21 Jul 2022
Cited by 1 | Viewed by 2150
Abstract
Structured light fields have attracted much attention due to rich spatial degrees of freedom. The tailoring of an arbitrary structured light field on demand is the precondition for the application of structured light. Therefore, the computer holography method used to reconstruct a coherent [...] Read more.
Structured light fields have attracted much attention due to rich spatial degrees of freedom. The tailoring of an arbitrary structured light field on demand is the precondition for the application of structured light. Therefore, the computer holography method used to reconstruct a coherent light field wavefront has been naturally applied for generating structured light. In this work, we comprehensively demonstrate the principles and procedures of pure-phase computer-generated holography (PP-CGH) and binary-amplitude computer-generated holography (BA-CGH) methods for tailoring structured light, realized by two digitally programmable devices: liquid-crystal spatial light modulators (Lc-SLM) and digital micromirror devices (DMD), respectively. Moreover, we first compare the two approaches in detail and clarify the recipe to obtain a high tailoring accuracy and efficiency, which will help researchers to better understand and utilize the holographic tailoring of structured optical fields. Full article
(This article belongs to the Special Issue Vortex Beams: Fundamentals and Applications)
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11 pages, 1969 KiB  
Article
Calibration of the Soleil–Babinet Compensator Based on the Vectorial Optical Field
by Yayun Ma, Fen Yang and Dong’e Zhao
Photonics 2022, 9(6), 416; https://doi.org/10.3390/photonics9060416 - 15 Jun 2022
Cited by 8 | Viewed by 2932
Abstract
The Soleil–Babinet compensator (SBC) is a variable retarder and has been used in a variety of application fields. A scheme based on the vectorial optical field is proposed to calibrate the SBC by transforming the change of the phase retardation into the visible [...] Read more.
The Soleil–Babinet compensator (SBC) is a variable retarder and has been used in a variety of application fields. A scheme based on the vectorial optical field is proposed to calibrate the SBC by transforming the change of the phase retardation into the visible rotation of the petal-like pattern. The relationship between the rotation angle of the petal-like pattern and the phase retardation of the SBC is established theoretically. In the experiment, the vector beam is generated by using the spiral phase plate (SPP) and the modified Mach–Zehnder interferometer based on the superposition principle of two orthogonal circularly polarized vortex beams with opposite topological charges. Taking advantage of the image processing method, the rotation angles of the acquired petal patterns are calculated, and the relationship between the phase retardation of the SBC and the displacements of its micrometer screw is determined. The measured phase retardation of the SBC ranges from −277.00° to 516.57°. By linearly fitting the experimental data, the phase sensitivity is 33.076 ± 0.147 °/mm, and the coefficient of determination value that shows the linearity of the experimental data is 0.9995. The experimental results agree well with the theoretical data. Full article
(This article belongs to the Special Issue Vortex Beams: Fundamentals and Applications)
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11 pages, 6033 KiB  
Communication
Mitigating Vortex Splitting by Controlling the Wavefront Isophase Line Curvature of Vector Autofocusing Airy Vortex Beams in Free Space
by Xu Yan, Shuang Liang, Jia Li and Lixin Guo
Photonics 2022, 9(5), 325; https://doi.org/10.3390/photonics9050325 - 9 May 2022
Cited by 2 | Viewed by 2004
Abstract
The match between the orbital angular momentum (OAM) transmission and receipt is a prerequisite for vortex beams as a carrier of the wireless optical communication system in free space. However, the vortex splitting induced by atmospheric turbulence results in an offset in the [...] Read more.
The match between the orbital angular momentum (OAM) transmission and receipt is a prerequisite for vortex beams as a carrier of the wireless optical communication system in free space. However, the vortex splitting induced by atmospheric turbulence results in an offset in the average OAM measured after propagating over the free space optical communication link. Therefore, how to reduce the vortex splitting effect to improve the stability of orbital angular momentum propagation is studied in this paper. First, a new parameter (m) is introduced to modulate the radial distribution of the polarization state of the autofocusing Airy vortex beams (AAVBs). Second, to control the optical field distribution in focal plane, the wavefront isophase line curvature of the AAVBs is reconstructed by using the Pancharatnam-Berry phase generated in the polarization conversion process. Finally, by comparing the vortex splitting rates of the AAVBs with different wavefrontisophase line curvatures under different turbulence environments, it can be found that the vortex splitting in free space can be effectively mitigated by choosing an appropriate wavefront isophase line curvature. In addition, the mitigation effect is more obvious in the atmosphere with stronger turbulence. This study provides a new feasible method to control the phase structure of vortex beams and promises potential applications in the OAM-based free space optical communication system. Full article
(This article belongs to the Special Issue Vortex Beams: Fundamentals and Applications)
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10 pages, 4557 KiB  
Communication
Collapse Dynamics of Vortex Beams in a Kerr Medium with Refractive Index Modulation and PT-Symmetric Lattices
by Gang Yao, Yuhua Li and Rui-Pin Chen
Photonics 2022, 9(4), 249; https://doi.org/10.3390/photonics9040249 - 10 Apr 2022
Cited by 5 | Viewed by 2009
Abstract
Using the two-dimensional nonlinear Schrödinger equation, the collapse dynamics of vortex beams in a Kerr medium with refractive index modulation and parity–time (PT) symmetric lattices are explored. The critical power for the collapse of vortex beams in a Kerr medium with real optical [...] Read more.
Using the two-dimensional nonlinear Schrödinger equation, the collapse dynamics of vortex beams in a Kerr medium with refractive index modulation and parity–time (PT) symmetric lattices are explored. The critical power for the collapse of vortex beams in a Kerr medium with real optical lattices (i.e., refractive index modulation lattices) was obtained and discussed. Numerical calculations showed that the number of self-focusing points, the locations of the collapse, and the propagation distances for collapse are sensitively dependent on the modulation factors, topological charge numbers, and initial powers. When the vortex optical field propagates in a Kerr medium with real optical lattices, the optical field will collapse into a symmetrical shape. However, the shape of the vortex beam will be chaotically distorted and collapse in asymmetric patterns during propagation in a Kerr medium with PT-symmetric lattices because of the presence of the complex refraction index. Introducing PT-symmetric lattices into nonlinear Kerr materials may offer a new approach to controlling the collapse of vortex beams. Full article
(This article belongs to the Special Issue Vortex Beams: Fundamentals and Applications)
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19 pages, 9889 KiB  
Article
Theoretical and Experimental Research on the Mode Modulation Regulation for the Mode-Tunable Vortex Laser Based on Mode Conversion and Intra-Cavity Modulation
by Shibing Lin, Deen Wang, Shaonan Kang, Yamin Zheng and Lei Huang
Photonics 2022, 9(4), 232; https://doi.org/10.3390/photonics9040232 - 1 Apr 2022
Cited by 2 | Viewed by 2287
Abstract
The vortex laser beam has been widely applied in many fields for its unique properties. However, researchers have to conduct extensive and recurring experiments to find the modulation abilities of the vortex beam modes for a given resonant cavity. In this paper, a [...] Read more.
The vortex laser beam has been widely applied in many fields for its unique properties. However, researchers have to conduct extensive and recurring experiments to find the modulation abilities of the vortex beam modes for a given resonant cavity. In this paper, a mode modulation regulation acquisition (MORA) method, investigating the relationship between the modes of the vortex beam and modulation parameters, is proposed and verified. A typical mode-tunable vortex laser, consisting of a classic plano-concave straight cavity, a vortex beam generation beamline, and a reference beam acquisition beamline, is used as the analysis and experiment object. The principle and working process of the MORA method is analyzed in the simulation, and its validity is verified in the experiment. Based on the obtained theoretical relationship between the modes of the vortex beam and modulation parameters, the MORA method could be used to help researchers in designing the practical vortex laser with target vortex beams output by optimizing the structure of the vortex laser, selecting the suitable intra-cavity modulation elements (IMEs), and pre-positioning the location of the IMEs. Full article
(This article belongs to the Special Issue Vortex Beams: Fundamentals and Applications)
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11 pages, 5131 KiB  
Communication
Controlling Dispersion Characteristic of Focused Vortex Beam Generation
by Xueshen Li and Zhigang Fan
Photonics 2022, 9(3), 179; https://doi.org/10.3390/photonics9030179 - 12 Mar 2022
Cited by 2 | Viewed by 2390
Abstract
As an important structured beam, vortex beams have a wide range of applications in many fields. However, conventional vortex beam generators require complex optical systems, and this problem is particularly serious with regards to focused vortex beam generators. The emergence of metasurfaces provides [...] Read more.
As an important structured beam, vortex beams have a wide range of applications in many fields. However, conventional vortex beam generators require complex optical systems, and this problem is particularly serious with regards to focused vortex beam generators. The emergence of metasurfaces provides a new idea for solving this problem; however, the accompanying chromatic dispersion limits its practical application. In this paper, we show that the dispersion characteristic of focused vortex beam generators based on metasurfaces can be controlled by simultaneously manipulating the geometric and propagative phases. The simulation results show that the transmission-type focused vortex beam generators exhibit positive dispersion, zero dispersion, and negative dispersion, respectively. This work paves the way for the practical application of focused vortex beam generators. Full article
(This article belongs to the Special Issue Vortex Beams: Fundamentals and Applications)
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19 pages, 7641 KiB  
Article
Topological Charge of Multi-Color Optical Vortices
by Victor Victorovich Kotlyar, Alexey Andreevich Kovalev, Anton Gennadyevich Nalimov and Sergey Sergeevich Stafeev
Photonics 2022, 9(3), 145; https://doi.org/10.3390/photonics9030145 - 28 Feb 2022
Cited by 4 | Viewed by 3068
Abstract
The topological charge of an optical vortex is a quantity rather stable against phase distortions, for example, turbulence. This makes the topological charge attractive for optical communications, but for many structured beams it is unknown. Here, we derive the topological charge (TC) of [...] Read more.
The topological charge of an optical vortex is a quantity rather stable against phase distortions, for example, turbulence. This makes the topological charge attractive for optical communications, but for many structured beams it is unknown. Here, we derive the topological charge (TC) of a coaxial superposition of spatially coherent Laguerre–Gaussian beams with different colors, each beam with its own wavelength and its own TC. It turns out that the TC of such a superposition equals the TC of the LG beam with a longer wavelength, regardless of the weight coefficient of this beam in the superposition and regardless of its TC. It is interesting that the instantaneous TC of such a superposition is conserved on propagation, whereas the time-averaged intensity distribution of the colored optical vortex changes its gamut; if, in the near field, the colors of the light rings arrange along the radius according to their TCs in the superposition from lower to greater, then, on space propagation, the colors of the light rings in the cross-section are arranged in reverse order from the greater TC to the lower TC. We also demonstrate that, by choosing appropriate wavelengths (blue, green, and red) in a three-color superposition of single-ringed LG beams, it is possible to generate, at some propagation distance, a time-averaged light ring of the white color. If all the beams in a three-color superposition of single-ringed LG beams have the same TC, then there is a single ring of nearly white light in the initial plane. Then, on propagation in space, light rings of different colors acquire different radii: a smaller ring radius for a shorter wavelength. Full article
(This article belongs to the Special Issue Vortex Beams: Fundamentals and Applications)
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Review

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15 pages, 32554 KiB  
Review
Advances on Solid-State Vortex Laser
by Zhichao Zhang, Lan Hai, Shiyao Fu and Chunqing Gao
Photonics 2022, 9(4), 215; https://doi.org/10.3390/photonics9040215 - 24 Mar 2022
Cited by 13 | Viewed by 3718
Abstract
Vortex beams (VBs) are structured beams with helical wavefronts carrying orbital angular momentum (OAM) and they have been widely used in lots of domains, such as optical data-transmission, optical tweezer, quantum entanglement, and super-resolution imaging. The ability to generate vortex beams with favorable [...] Read more.
Vortex beams (VBs) are structured beams with helical wavefronts carrying orbital angular momentum (OAM) and they have been widely used in lots of domains, such as optical data-transmission, optical tweezer, quantum entanglement, and super-resolution imaging. The ability to generate vortex beams with favorable performance is of great significance for these advanced applications. Compared with extra-cavity schemes, such as spatial light modulation, mode conversion, and others which transform other modes into vortex modes, solid-state vortex lasers can output vortex beams directly and show advantages including a compact structure, high robustness, easy to integrate, and low cost. In this review, we summarize intra-cavity generation approaches to vortex beams in solid-state lasers. Our work on 1.6μm eye-safe vector vortex lasers is also introduced. Full article
(This article belongs to the Special Issue Vortex Beams: Fundamentals and Applications)
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