scholarly journals Optical trapping of the low index of refraction particles by focused vortex beams and two face-to-face focused beams

2020 ◽  
Vol 50 (3) ◽  
Author(s):  
Meiling Duan ◽  
Hanghang Zhang ◽  
Jinhong Li
Keyword(s):  
Optical Trapping ◽  
Rayleigh Scattering ◽  
Dimensional Space ◽  
Focal Length ◽  
Index Of Refraction ◽  
Gradient Force ◽  
Vortex Beam ◽  
Face To Face ◽  
Transverse Gradient ◽  
Vortex Beams

Using the extended Huygens–Fresnel principle and Rayleigh scattering theory, optical trapping of the low index of refraction particles using a focused Gaussian Schell-model (GSM) non-vortex beam, a focused GSM vortex beam, and two face-to-face focused GSM vortex beams have been studied. The results demonstrate that the focused GSM non-vortex beam cannot capture the low index of refraction particles, however, the focused GSM vortex beam can be a two-dimensional trap of particles in the z-axis, and the transverse gradient force Fgrad,x and the trapping equilibrium region increase as the topological charge m increases. As the focal length f or the refractive index of particles np decreases, the radiation forces increase and the trapping ability also enhances. To trap the low index particles in three-dimensional space, we adopt that the two face-to-face focused GSM vortex beams can be used to construct an optical potential well. The transverse gradient force of two face-to-face focused GSM vortex beams is twice that of a single GSM vortex beam. The limit of the radius for the low index of refraction particles that were stably captured has also been determined. The obtained results provide valuable information for trapping and manipulating the low index of refraction particles using GSM vortex beams, which may be applied in micromanipulation, biotechnology, nanotechnology and so on.

scholarly journals Arbitrary polarization conversion for pure vortex generation with a single metasurface

Nanophotonics ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 727-732
Author(s):  
Marco Piccardo ◽  
Antonio Ambrosio
Keyword(s):  
Angular Momentum ◽  
Polarization Conversion ◽  
Vortex Beam ◽  
Vortex Generation ◽  
Optical Elements ◽  
Amplitude Control ◽  
Cavity Resonators ◽  
Vortex Beams ◽  
Topological Charges ◽  
Selection Of

AbstractThe purity of an optical vortex beam depends on the spread of its energy among different azimuthal and radial modes, also known as $\ell $- and p-modes. The smaller the spread, the higher the vortex purity and more efficient its creation and detection. There are several methods to generate vortex beams with well-defined orbital angular momentum, but only few exist allowing selection of a pure radial mode. These typically consist of many optical elements with rather complex arrangements, including active cavity resonators. Here, we show that it is possible to generate pure vortex beams using a single metasurface plate—called p-plate as it controls radial modes—in combination with a polarizer. We generalize an existing theory of independent phase and amplitude control with birefringent nanopillars considering arbitrary input polarization states. The high purity, sizeable creation efficiency, and impassable compactness make the presented approach a powerful complex amplitude modulation tool for pure vortex generation, even in the case of large topological charges.

scholarly journals Transparent Metasurface for Generating Microwave Vortex Beams with Cross-Polarization Conversion

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2448 ◽  
Author(s):  
Hongyu Shi ◽  
Luyi Wang ◽  
Mengran Zhao ◽  
Juan Chen ◽  
Anxue Zhang ◽  
...  
Keyword(s):  
Transmission Loss ◽  
Phase Distribution ◽  
Polarization Conversion ◽  
Vortex Beam ◽  
Cross Polarization ◽  
Measurement Results ◽  
Vortex Beams ◽  
Simulation Results ◽  
Polarization Level ◽  
Transmission Phase

In this paper, metasurfaces with both cross-polarization conversion and vortex beam-generating are proposed. The proposed finite metasurface designs are able to change the polarization of incident electromagnetic (EM) waves to its cross-polarization. In addition, they also can modulate the incidences into beams carrying orbital angular momentum (OAM) with different orders ( l = + 1 , l = + 2 , l = − 1 and l = − 2 ) by applying corresponding transmission phase distribution schemes on the metasurface aperture. The generated vortex beams are at 5.14 GHz. The transmission loss is lower than 0.5 dB while the co-polarization level is −10 dB compared to the cross-polarization level. The measurement results confirmed the simulation results and verified the properties of the proposed designs.

Optical Trapping of Low Refractive Index Particles by Dual Vortex Beams

2021 ◽  
Author(s):  
Sho Nakaya ◽  
Yuichi Kozawa ◽  
Yuuki Uesugi ◽  
Shunichi Sato
Keyword(s):  
Refractive Index ◽  
Optical Trapping ◽  
Vortex Beams ◽  
Low Refractive Index

Multi-channeled vortex beam switch with moiré metasurfaces

2021 ◽  
Author(s):  
Cheng Cui ◽  
Zheng Liu ◽  
Bin Hu ◽  
Yurong Jiang ◽  
Juan Liu
Keyword(s):  
Functional Diversity ◽  
Optical Communications ◽  
Topological Charge ◽  
Signal Transmission ◽  
Polarized Light ◽  
Vortex Beam ◽  
Practical Applications ◽  
Linearly Polarized ◽  
Vortex Beams ◽  
Topological Charges

Abstract Tunable metasurface devices are considered to be an important link for metasurfaces to practical applications due to their functional diversity and high adaptability to the application scenarios. Metasurfaces have unique value in the generation of vortex beams because they can realize light wavefronts of any shape. In recent years, several vortex beam generators using metasurfaces have been proposed. However, the topological charge generally lacks tunability, which reduces the scope of their applications. Here, we propose an active tunable multi-channeled vortex beam switch based on a moiré structure composed of two cascaded dielectric metasurfaces. The simulation results show that when linearly polarized light with a wavelength of 810 nm is incident, the topological charge from -6 to +6 can be continuously generated by relatively rotating the two metasurfaces. Meanwhile, different topological charges are deflected to different spatial channels, realizing the function of multi-channeled signal transmission. We also study the efficiency and broadband performance of the structure. The proposed multi-channeled separation method of vortex beams that can actively tune topological charges paves the way for the compactness and functional diversity of devices in the fields of optical communications, biomedicine, and optoelectronics.

scholarly journals Real-Time Mode Switching and Beam Scanning of High-Gain OAM Waves Using a 1-Bit Reconfigurable Reflectarray Antenna

Electronics ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 2181
Author(s):  
Ziyang Wang ◽  
Xiaotian Pan ◽  
Fan Yang ◽  
Shenheng Xu ◽  
Maokun Li
Keyword(s):  
Real Time ◽  
Dimensional Space ◽  
Large Angle ◽  
High Gain ◽  
Mode Switching ◽  
Effective Control ◽  
Vortex Beam ◽  
Beam Scanning ◽  
The Future ◽  
Reflectarray Antenna

A reconfigurable electromagnetic surface has been studied to realize the adjustable orbital angular momentum (OAM) beams for real-time wireless communication and dynamic target detection in the future. OAM mode switching realized by many previous designs suffers from low gains without OAM beam scanning. In this article, a 1-bit reconfigurable reflectarray antenna is designed, fabricated, and tested for the real-time control of OAM mode switching and large-angle vortex beam scanning in three-dimensional space. The proposed reflectarray surface is composed of 1-bit electronically reconfigurable cells, and the size is 24 λ × 24 λ with 2304 units. The reconfigurable element is designed by using a radiation patch loading a PIN diode with effective control of two states, “ON” and “OFF”, for the demand of 180° phase difference. The reflectarray surface can be assigned to a code sequence of 0 or 1 by the Field-Programmable Gate Array (FPGA) in real time. Henceforth, the coding surface can dynamically control the generation of high-gain OAM beams, where only the optimized phase distributions on the surface need to be changed according to demand. To verify the concept, a large-scale reflectarray surface is fabricated and measured with an oblique feed at 15°. Different OAM-carrying phase distributions for different OAM beam states are calculated and tested. The test results show that the OAM mode switching between l = 1 and l = 2 is realized, and other variable modes such as l = 3 or l = 5 can also be achieved by modifying the phase encoding sequence. Furthermore, the direction of the vortex beams can be accurately controlled with gains over 20 dBi, and the large-angle vortex beam scanning is verified. Therefore, all results demonstrate that the proposed 1-bit reconfigurable reflectarray is efficient for the regulation and control of OAM-carrying beams for the demand of real-time dynamic wireless communications in the future.

scholarly journals Vortex Beam Encoded All-Optical Logic Gates Based on Nano-Ring Plasmonic Antennas

Nanomaterials ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1649
Author(s):  
Houquan Liu ◽  
Hongchang Deng ◽  
Shijie Deng ◽  
Chuanxin Teng ◽  
Ming Chen ◽  
...  
Keyword(s):  
Logic Gate ◽  
Logic Gates ◽  
Vortex Beam ◽  
Optical Logic ◽  
Optical Elements ◽  
Optical Logic Gates ◽  
Input Signals ◽  
All Optical ◽  
Vortex Beams ◽  
Polarization States

Vortex beam encoded all-optical logic gates are suggested to be very important in future information processing. However, within current logic devices, only a few are encoded by using vortex beams and, in these devices, some space optical elements with big footprints (mirror, dove prism and pentaprism) are indispensable components, which is not conducive to device integration. In this paper, an integrated vortex beam encoded all-optical logic gate based on a nano-ring plasmonic antenna is proposed. In our scheme, by defining the two circular polarization states of the input vortex beams as the input logic states and the normalized intensity of the plasmonic field at the center of the nano-ring as the output logic states, OR and AND (NOR and NAND) logic gates are realized when two 1st (1st) order vortex beams are chosen as the two input signals; and a NOT logic gate is obtained when one 1st order vortex beam is chosen as the input signal. In addition, by defining the two linear polarization states (x and y polarization) of the input vortex beams as the two input logic states, an XNOR logic gate is realized when two 1st order vortex beams are chosen as the two input signals.

Detecting the topological charge of a vortex beam by an arc slit diffraction

2017 ◽  
Vol 31 (23) ◽  
pp. 1750172 ◽  
Author(s):  
Dongzhi Fu ◽  
Hailong Zhou ◽  
Kaiwei Wang ◽  
Pei Zhang ◽  
Jianji Dong ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Diffraction Pattern ◽  
Orbital Angular Momentum ◽  
Topological Charge ◽  
Light Spot ◽  
Far Field ◽  
Vortex Beam ◽  
Efficient Measurement ◽  
Vortex Beams

The simple and efficient measurement of the light orbital angular momentum (OAM) is essential to both the classical and quantum applications with vortex beams. Here, we study the diffraction pattern in the far field when a vortex beam passes through an arc slit and demonstrate experimentally that a light spot of the diffraction pattern has a displacement which is linear to the topological charge (TC) of the incident vortex beam. Based on this property, this method is capable of measuring both modulus and sign of TC of the vortex beam. Furthermore, this scheme allows identifying multiple OAM states simultaneously.

scholarly journals GEOMETRICAL APPROACH TO LIGHT IN INHOMOGENEOUS MEDIA

2002 ◽  
Vol 17 (11) ◽  
pp. 1543-1558 ◽  
Author(s):  
P. PIWNICKI
Keyword(s):  
Electromagnetic Fields ◽  
Light Propagation ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Flat Space ◽  
Dielectric Medium ◽  
Index Of Refraction ◽  
Geometrical Approach ◽  
Complex Formulation ◽  
Relativistic Approach

Electromagnetism in an inhomogeneous dielectric medium at rest is described using the methods of differential geometry. In contrast to a general relativistic approach the electromagnetic fields are discussed in three-dimensional space only. The introduction of an appropriately chosen three-dimensional metric leads to a significant simplification of the description of light propagation in an inhomogeneous medium: light rays become geodesics of the metric and the field vectors are parallel transported along the rays. The new metric is connected to the usual flat space metric diag[1,1,1] via a conformal transformation leading to new, effective values of the medium parameters [Formula: see text] and [Formula: see text] with [Formula: see text]. The corresponding index of refraction is thus constant and so is the effective velocity of light. Space becomes effectively empty but curved. All deviations from straight-line propagation are now due to curvature. The approach is finally used for a discussion of the Riemann–Silberstein vector, an alternative, complex formulation of the electromagnetic fields.

scholarly journals On-Column 2p Bound State with Topological Charge ±1 Excited by an Atomic-Size Vortex Beam in an Aberration-Corrected Scanning Transmission Electron Microscope

2012 ◽  
Vol 18 (4) ◽  
pp. 711-719 ◽  
Author(s):  
Huolin L. Xin ◽  
Haimei Zheng
Keyword(s):  
Topological Charge ◽  
Bound States ◽  
Numerical Solutions ◽  
Incident Beam ◽  
Vortex Beam ◽  
Phase Front ◽  
Atomic Size ◽  
Convergence Angle ◽  
Vortex Beams ◽  
Energy Convergence

AbstractAtomic-size vortex beams have great potential in probing the magnetic moment of materials at atomic scales. However, the limited depth of field of vortex beams constrains the probing depth in which the helical phase front is preserved. On the other hand, electron channeling in crystals can counteract beam divergence and extend the vortex beam without disrupting its topological charge. Specifically, in this article, we report that atomic vortex beams with topological charge ±1 can be coupled to the 2p columnar bound states and propagate for more than 50 nm without being dispersed and losing its helical phase front. We give numerical solutions to the 2p columnar orbitals and tabulate the characteristic size of the 2p states of two typical elements, Co and Dy, for various incident beam energies and various atomic densities. The tabulated numbers allow estimates of the optimal convergence angle for maximal coupling to 2p columnar orbital. We have also developed analytic formulae for beam energy, convergence angle, and hologram-dependent scaling for various characteristic sizes. These length scales are useful for the design of pitch-fork apertures and operations of microscopes in the vortex-beam imaging mode.

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