Holographic-Inspired Multiple Circularly Polarized Vortex-Beam Generation with Flexible Topological Charges and Beam Directions (original) (raw)
Related papers
Generation of E-band metasurface-based vortex beam with reduced divergence angle
Scientific Reports
Vortex beams carrying orbital angular momentum (OAM) have attracted considerable attention for the development of high-capacity wireless communication systems due to their infinite sets of orthogonal modes. However, the practical applications of Laguerre-Gaussian type vortex beams are limited due to the fact that the divergence angle increases as the order of the OAM mode increases. In this work, we present metasurfaces that generate vortex beams carrying OAM modes with reduced divergence angles in the E-band frequency range. The metasurfaces were designed using eight different meta-atom phase elements, including a spiral phase distribution for OAM modes l = 1 and 2, a phase gradient array to avoid interference with the source beam, and a lens pattern array to reduce the divergence angle. Through simulation and experimental measurement, it was confirmed that the divergence angle of the vortex beam generated by the metasurface with the lens pattern was reduced from 13° to 9° and 14° ...
High-Purity Multi-Mode Vortex Beam Generation With Full Complex-Amplitude-Controllable Metasurface
IEEE Transactions on Antennas and Propagation, 2023
Vortex beam with inherent orbital angular momentum (OAM) is promising in high-capacity communication. On multimode vortex beam generation, metasurface has shown exceptional advantages of integration and miniaturization. For the current widely used phase-only methods on multimode vortex beam generation by metasurface, the purity of the OAM-mode spectrum is severely affected. A new method for generation of multimode vortex beam with high mode purity is proposed in this article by reconstructing the complete complex amplitude information on the meta-device aperture. A 20 dB suppression of the crosstalk modes is experimentally observed for the co-directional multimode vortex beam generation, which is much improved compared to the traditional phase-only scheme. In addition, the proposed scheme also provides the capability of generating highpurity multimode vortex beams with arbitrary preset propagation directions and power allocations. This study provides a platform for high-performance vortex beam communication by increasing the signal-to-noise ratio and enabling the multicasting scenarios with customized capacity requirements.
Journal of the Optical Society of America B, 2015
A novel method of generation and synthesis of azimuthally E-polarized vortex beams is presented. Along the axis of propagation such beams have a strong longitudinally polarized magnetic field where ideally there is no electric field. We show how these beams can be constructed through the interference of Laguerre-Gaussian beams carrying orbital angular momentum. As an example, we present a metasurface made of double-split ring slot pairs and report a good agreement between simulated and analytical results. Both a high magnetic-to-electric-field contrast ratio and a magnetic field enhancement are achieved. We also investigate the metasurface physical constraints to convert a linearly polarized beam into an azimuthally E-polarized beam and characterize the performance of magnetic field enhancement and electric field suppression of a realistic metasurface. These findings are potentially useful for novel optical spectroscopy related to magnetic dipolar transitions and for optical manipulation of particles with spin and orbital angular momentum.
2014
A novel method of generation and synthesis of azimuthally E-polarized vortex beams is presented. Along the axis of propagation such beams have a strong longitudinally polarized magnetic field where ideally there is no electric field. We show how these beams can be constructed through the interference of Laguerre-Gaussian beams carrying orbital angular momentum. As an example, we present a metasurface made of double-split ring slot pairs and report a good agreement between simulated and analytical results. Both a high magnetic-to-electric-field contrast ratio and a magnetic field enhancement are achieved. We also investigate the metasurface physical constraints to convert a linearly polarized beam into an azimuthally E- polarized beam and characterize the performance of magnetic field enhancement and electric field suppression of a realistic metasurface. These findings are potentially useful for novel optical spectroscopy related to magnetic dipolar transitions and for optical manipu...
Multichannel terahertz quasi-perfect vortex beams generation enabled by multifunctional metasurfaces
Nanophotonics
Vortex beams carrying orbital angular momentum (OAM) open a new perspective in various terahertz research. Multichannel and divergence controllable terahertz vortex beam generation holds the key to promoting the development of OAM related terahertz research. Here, we introduced and experimentally demonstrated quasi-perfect vortex beam (Q-PVB) with a controllable divergence angle independent of the topological charge and multichannel Q-PVBs generation with all-dielectric multifunctional metasurfaces. By superimposing specific phase functions together into the metasurfaces, multiple vortex beams and four-channel Q-PVBs with different topological charges are generated as well as focused at separated positions. High resolution characterization of terahertz electric field shows the good quality and broadband properties of Q-PVBs. Interestingly, compared with conventional perfect vortex beam; Q-PVB displays a smaller divergence angle and thinner ring width. The metasurfaces proposed here ...
Polarization-Encrypted Orbital Angular Momentum Multiplexed Metasurface Holography
ACS Nano
Metasurface holography has the advantage of realizing complex wavefront modulation by thin layers together with the progressive technique of computer-generated holographic imaging. Despite the well-known light parameters, such as amplitude, phase, polarization, and frequency, the orbital angular momentum (OAM) of a beam can be regarded as another degree of freedom. Here, we propose and demonstrate orbital angular momentum multiplexing at different polarization channels using a birefringent metasurface for holographic encryption. The OAM selective holographic information can only be reconstructed with the exact topological charge and a specific polarization state. By using an incident beam with different topological charges as erasers, we mimic a super-resolution case for the reconstructed image, in analogy to the well-known STED technique in microscopy. The combination of multiple polarization channels together with the orbital angular momentum selectivity provides a higher security level for holographic encryption. Such a technique can be applied for beam shaping, optical camouflage, data storage, and dynamic displays.
Control of Orbital Angular Momentum Regimen by Modulated Metasurface Leaky-Wave Antennas
arXiv (Cornell University), 2021
In this paper, we present the design procedure of modulated metasurface leaky-wave antennas (MMLWAs) to generate coaxial superposition of vortex beams with several orbital angular momentum (OAM) states. Based on the Flat Optics (FO) technique and aperture field estimation (AFE) method, an analytical framework is proposed to facilitate the implementation of MMLWAs generating multiple topological charges in the OAM regimen. Furthermore, using the spectral analysis which has been derived from the proposed model, we have shown that the symmetry of aperture shape can affect the purity of the mode. Also the perfectly symmetric circular shape is introduced as an ideal choice for high-purity vortex generation. This single aperture antenna with embedded monopole feed can be an appropriate alternative to more complex vortex beam generators such as spiral phase plates and circular antenna arrays.
Beam-Editing Coding Metasurfaces Based on Polarization Bit and Orbital-Angular-Momentum-Mode Bit
Advanced Optical Materials, 2017
Coding Metasurfaces Recently, orbital angular momentum (OAM) vortex waves, [1] have occupied wide attention, attributed to their excellent performance and various applications, such as in optics and optical communication. [2,3] The OAM technology allows information to be transmitted in the same beam with low crosstalk, [2,4,5] which improves the communication capability significantly. However, this technology has also some weaknesses, [6] such as the limited transmitting distance limitation. The radio OAM simulations and experiments have been performed successively, [7,8] which demonstrated potential applications in radio frequencies.
Optical Materials Express, 2019
Metasurfaces, the two-dimensional (2D) metamaterials, facilitate the implementation of abrupt phase discontinuities using an array of ultrathin and subwavelength features. These metasurfaces are considered as one of the propitious candidates for realization and development of miniaturized, surface-confined, and flat optical devices. This is because of their unprecedented capabilities to engineer the wavefronts of electromagnetic waves in reflection or transmission mode. The transmission-type metasurfaces are indispensable as the majority of optical devices operate in transmission mode. Along with other innovative applications, previous research has shown that Optical-Vortex (OV) generators based on transmission-type plasmonic metasurfaces overcome the limitations imposed by conventional OV generators. However, significant ohmic losses and the strong dispersion hampered the performance and their integration with state-ofthe-art technologies. Therefore, a high contrast all-dielectric metasurface provides a compact and versatile platform to realize the OV generation. The design of this type of metasurfaces relies on the concept of Pancharatnam-Berry (PB) phase aiming to achieve a complete 2π phase control of a spin-inverted transmitted wave. Here, in this paper, we present an ultrathin, highly efficient, all-dielectric metasurface comprising nano-structured silicon on a quartz substrate. With the help of a parameter-sweep optimization, a nanoscale spatial resolution is achieved with a cross-polarized transmission efficiency as high as 95.6% at an operational wavelength of 1.55 µm. Significantly high cross-polarized transmission efficiency has been achieved due to the excitation of electric quadrupole resonances with a very high magnitude. The highly efficient control over the phase has enabled a riveting optical phenomenon. Specifically, the phase profiles of two distinct optical devices, a lens and Spiral-Phase-Plate (SPP), can be merged together, thus producing a highly Focused-Optical-Vortex (FOV) with a maximum focusing efficiency of 75.3%.
Terahertz Dual-Band Dual-Polarization 3-Bit Coding Metasurface for Multiple Vortex Beams Generation
Electronics
Terahertz technology and vortex beams have demonstrated powerful capabilities in enhancing the channel capacity of communication systems. This work proposes a design strategy of dual-band and dual-function 3-bit coding metasurface based on beam polarization characteristics. The unit cell of the metasurface is composed of two pattern structures, which has the ability to flexibly and independently control the reflection phases of incident plane wave at two frequency bands. The metasurface designed in this work is a combination of two patterns according to the addition operation and the convolution operation. The 3-bit coding metasurface generates two orbital angular momentum (OAM) beams with a deflection of 12.1° with modes l1=+1 and l2=−1 under the y-polarized incidence at 0.6 THz. Similarly, the designed metasurface produces two OAM beams with a deflection of 16.5° under the incidence of x-polarized wave at 0.9 THz, and the modes are l3=+1 and l4=−2. The full-wave simulation results...