scholarly journals Phyllotaxis-inspired nanosieves with multiplexed orbital angular momentum

eLight ◽  
2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Zhongwei Jin ◽  
David Janoschka ◽  
Junhong Deng ◽  
Lin Ge ◽  
Pascal Dreher ◽  
...  
Keyword(s):  
Free Space ◽  
High Capacity ◽  
Vortex Generator ◽  
Optical Vortex ◽  
Optical Vortices ◽  
Time Resolved ◽  
Optical Applications ◽  
On Chip ◽  
Pine Cones ◽  
Meta Atom

AbstractNanophotonic platforms such as metasurfaces, achieving arbitrary phase profiles within ultrathin thickness, emerge as miniaturized, ultracompact and kaleidoscopic optical vortex generators. However, it is often required to segment or interleave independent sub-array metasurfaces to multiplex optical vortices in a single nano-device, which in turn affects the device’s compactness and channel capacity. Here, inspired by phyllotaxis patterns in pine cones and sunflowers, we theoretically prove and experimentally report that multiple optical vortices can be produced in a single compact phyllotaxis nanosieve, both in free space and on a chip, where one meta-atom may contribute to many vortices simultaneously. The time-resolved dynamics of on-chip interference wavefronts between multiple plasmonic vortices was revealed by ultrafast time-resolved photoemission electron microscopy. Our nature-inspired optical vortex generator would facilitate various vortex-related optical applications, including structured wavefront shaping, free-space and plasmonic vortices, and high-capacity information metaphotonics.

scholarly journals High-Efficiency All-Dielectric Metasurfaces for the Generation and Detection of Focused Optical Vortex for the Ultraviolet Domain

2020 ◽  
Vol 10 (16) ◽  
pp. 5716
Author(s):  
Ziheng Zhang ◽  
Tong Li ◽  
Xiaofei Jiao ◽  
Guofeng Song ◽  
Yun Xu
Keyword(s):  
High Performance ◽  
High Efficiency ◽  
Dielectric Material ◽  
Optical Vortex ◽  
Magnetic Dipoles ◽  
Half Wave ◽  
Potential Applications ◽  
On Chip ◽  
High Flexibility ◽  
Meta Atom

The optical vortex (OV) has drawn considerable attention owing to its tremendous advanced applications, such as optical communication, quantum entanglement, and on-chip detectors. However, traditional OV generators suffer from a bulky configuration and limited performance, especially in the ultraviolet range. In this paper, we utilize a large bandgap dielectric material, niobium pentoxide (Nb2O5), to construct ultra-thin and compact transmission-type metasurfaces to generate and detect the OV at a wavelength of 355 nm. The meta-atom, which operates as a miniature half-wave plate and demonstrates a large tolerance to fabrication error, manipulates the phase of an incident right-handed circular polarized wave with high cross-polarized conversion efficiency (around 86.9%). The phase delay of π between the orthogonal electric field component is attributed to the anti-parallel magnetic dipoles induced in the nanobar. Besides, focused vortex generation (topological charge l from 1 to 3) and multichannel detection (l from −2 to 2) are demonstrated with high efficiency, up to 79.2%. We envision that our devices of high flexibility may have potential applications in high-performance micron-scale integrated ultraviolet nanophotonics and meta-optics.

scholarly journals Birth of optical vortices in propagating fields with an original fractional topological charge

2020 ◽  
Vol 44 (4) ◽  
pp. 493-500
Author(s):  
A.A. Kovalev ◽  
A.P. Porfirev
Keyword(s):  
Angular Momentum ◽  
Free Space ◽  
Topological Charge ◽  
Random Phase ◽  
Phase Variation ◽  
Optical Vortex ◽  
Optical Vortices ◽  
Integer Number ◽  
Weak Phase ◽  
Phase Distortions

In contrast to the orbital angular momentum (OAM), which is conserved on free space propagation, the topological charge (TC) of a paraxial optical vortex (OV) is not conserved in the general case. Here, we investigate a Gaussian beam with a fractional TC in the original plane and demonstrate both theoretically and numerically how the TC changes in the course of propagation. Depending on the proximity of the topological charge to an even or odd integer number, an optical vortex with the original fractional TC is shown to behave in a number of different ways. For simple OVs (Laguerre-Gaussian or Bessel-Gaussian modes), TC is conserved both in propagation and after weak phase distortions. An experiment shows that when scattered by a random phase screen, the integer TC of an OV is conserved right up to a random phase variation of π. Therefore, in the case of weak turbulences, it is expedient to measure a discretely varying TC instead of a continuously varying OAM.

scholarly journals Optical Vortices: 3D Optical Vortex Lattices (Ann. Phys. 7/2021)

2021 ◽  
Vol 533 (7) ◽  
pp. 2170023
Author(s):  
Denis A. Ikonnikov ◽  
Sergey A. Myslivets ◽  
Vasily G. Arkhipkin ◽  
Andrey M. Vyunishev
Keyword(s):  
Optical Vortex ◽  
Optical Vortices ◽  
Vortex Lattices

scholarly journals Perspectives on advances in high-capacity, free-space communications using multiplexing of orbital-angular-momentum beams

APL Photonics ◽  
2021 ◽  
Vol 6 (3) ◽  
pp. 030901
Author(s):  
Alan E. Willner ◽  
Zhe Zhao ◽  
Cong Liu ◽  
Runzhou Zhang ◽  
Haoqian Song ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Orbital Angular Momentum ◽  
Free Space ◽  
High Capacity ◽  
Space Communications

scholarly journals Influence of attenuation on the generation of optical vortices in multihelicoidal optical fibers

2021 ◽  
Vol 2103 (1) ◽  
pp. 012149
Author(s):  
C N Alexeyev ◽  
S S Alieva ◽  
E V Barshak ◽  
B P Lapin ◽  
M A Yavorsky
Keyword(s):  
Optical Fibers ◽  
Fundamental Mode ◽  
Optical Vortex ◽  
Conversion Process ◽  
Exceptional Point ◽  
Optical Vortices ◽  
Attenuation Coefficients ◽  
Enhanced Sensitivity ◽  
Scalar Approximation ◽  
The Difference

Abstract In this paper we have studied influence of attenuation on conversion processes of the fundamental mode (FM) in multihelicoidal optical fibers (MHF) in the vicinity of the point of accidental spectrum degeneracy within the framework of the scalar approximation. To this end, we have obtained expressions for modes of the MHF, which consist of the FM and an optical vortex (OV), and shown that conversion of the FM into the OV takes place. The difference in the attenuation coefficients for the partial fields of MHF’s modes leads to deterioration in the conversion process even with an ideal system’s tuning. At sufficiently large values of attenuation coefficients the conversion of the incoming FM into the vortex vanishes. Also we have shown the presence of exceptional point (EP) in the spectra of modes of the MHF and demonstrated enhanced sensitivity of the fiber in the vicinity of the EP to perturbations.

Magnetic modulation of Fano resonances in optically thin terahertz superlattice metasurfaces

2021 ◽  
Author(s):  
Subhajit Karmakar ◽  
Ravi Varshney ◽  
Dibakar Roy Chowdhury
Keyword(s):  
Magnetic Field ◽  
Free Space ◽  
Skin Depth ◽  
Electromagnetic Energy ◽  
Magnetic Control ◽  
Fano Resonances ◽  
Electromagnetic Responses ◽  
On Chip ◽  
Magneto Resistance ◽  
Sub Wavelength

Abstract Optically thin metasurfaces operating at sub-skin depth thicknesses are intriguing because of its associated low plasmonic losses (compared to optically thick, beyond skin-depth metasurfaces). However, their applicability has been restricted largely because of reduced free space coupling with incident radiations resulting in limited electromagnetic responses. To overcome such limitations, we propose enhancement of effective responses (resonances) in sub-skin depth metasurfaces through incorporation of magneto-transport (Giant Magneto Resistance, GMR) concept. Here, we experimentally demonstrate dynamic magnetic modulation of structurally asymmetric metasurfaces (consisting of superlattice arrangement of thin (~ 10 nm each) magnetic (Ni)/ nonmagnetic (Al) layers) operating at terahertz (THz) domain. With increasing magnetic field (applied from 0 to 30 mT approximately, implies increasing superlattice conductivity), we observe stronger confinement of electromagnetic energy at the resonances (both in dipole and Fano modes). Therefore, this study introduces unique magnetically reconfigurable ability in Fano resonant THz metamaterials, which directly improves its performances operating in the sub-skin depth regime. Our study can be explained by spin-dependent terahertz magneto-transport phenomena in metals and can stimulate the paradigm for on-chip spin-based photonic technology enabling dynamic magnetic control over compact, sub-wavelength, sub-skin depth metadevices.

Turbulence-resilient high-capacity free-space optical communication

2021 ◽  
Author(s):  
Ziyi Zhu ◽  
Alexander Fyffe ◽  
Yiyu Zhou ◽  
Gerd Leuchs ◽  
Robert W. Boyd ◽  
...  
Keyword(s):  
Optical Communication ◽  
Free Space ◽  
High Capacity ◽  
Free Space Optical Communication ◽  
Free Space Optical ◽  
Space Optical Communication

Digitized subwavelength surface structure on silicon platform for wavelength-/polarization-/charge-diverse optical vortex generation

2020 ◽  
Author(s):  
Xiaoping Cao ◽  
Nan Zhou ◽  
Shuang Zheng ◽  
Shengqian Gao ◽  
Yuntao Zhu ◽  
...  
Keyword(s):  
Surface Structure ◽  
Optical Communications ◽  
Vortex Generator ◽  
Optical Vortex ◽  
Vortex Generation ◽  
Worst Case ◽  
Additional Degree ◽  
Direct Binary Search ◽  
Polarization Charge ◽  
Narrow Bandwidth

Abstract Optical vortices carrying orbital angular momentum (OAM) have recently attracted increasing interest for providing an additional degree of freedom for capacity scaling in optical communications. The optical vortex generator is an essential component to facilitate OAM-enabled optical communications. Traditional devices face challenges of limited compactness, narrow bandwidth and first-order OAM modes. Here, using the direct-binary search (DBS) optimization algorithm, we design, fabricate and demonstrate a digitized subwavelength surface structure on silicon platform for wavelength-/polarization-/charge-diverse optical vortex generation. It features an ultra-compact footprint (~3.6×3.6 μm 2 ) and ultra-wide bandwidth (1480-1630 nm), supporting two polarizations and high-order OAM modes (OAM +1 , OAM -1 , OAM +2 , OAM -2 ) with high purity of ~90%. The mode crosstalk matrix is measured in the experiment with favorable performance. When generating x-pol. OAM +1 , x-pol. OAM -1 , y-pol. OAM +1 and y-pol. OAM -1 , the crosstalk of the worst case is less than -14 dB. When generating OAM +1 , OAM -1 , OAM +2 and OAM -2 , the crosstalk between any two OAM modes is less than -10 dB, and the lowest crosstalk is about -17 dB. The wavelength-/polarization-/charge-diverse optical vortex generator enables the full access of multiple physical dimensions (wavelength, polarization, space) of lightwaves. The demonstrations may open up new perspectives for chip-scale solutions to multi-dimensional multiplexing optical communications.

scholarly journals Strongly Focused Circularly Polarized Optical Vortices Regulated by a Fractal Conical Lens

2019 ◽  
Vol 10 (1) ◽  
pp. 28
Author(s):  
Zhirong Liu ◽  
Kelin Huang ◽  
Anlian Yang ◽  
Xun Wang ◽  
Philip H. Jones
Keyword(s):  
Angular Momentum ◽  
Optical Tweezers ◽  
Numerical Aperture ◽  
Optical Element ◽  
Optical Vortex ◽  
Optical Vortices ◽  
Circularly Polarized ◽  
Strong Focusing ◽  
New Type ◽  
Vortex Beams

In this paper, a recently-proposed pure-phase optical element, the fractal conical lens (FCL), is introduced for the regulation of strongly-focused circularly-polarized optical vortices in a high numerical aperture (NA) optical system. Strong focusing characteristics of circularly polarized optical vortices through a high NA system in cases with and without a FCL are investigated comparatively. Moreover, the conversion between spin angular momentum (SAM) and orbital angular momentum (OAM) of the focused optical vortex in the focal vicinity is also analyzed. Results revealed that a FCL of different stage S could significantly regulate the distributions of tight focusing intensity and angular momentum of the circularly polarized optical vortex. The interesting results obtained here may be advantageous when using a FCL to shape vortex beams or utilizing circularly polarized vortex beams to exploit new-type optical tweezers.

Sign in / Sign up

Export Citation Format

Share Document