Generating and analyzing non-diffracting vector vortex beams (original) (raw)
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Hybrid generation and analysis of vector vortex beams
Applied optics, 2017
A method is described for generating optical vector vortex beams carrying superpositions of orbital angular momentum states by using a tandem application of a spatial light modulator with a vortex retarder. The vortex component has a spatially inhomogeneous phase front that can carry orbital angular momentum, and the vector nature is a spatially inhomogeneous state of polarization in the laser beam profile. The vector vortex beams are characterized experimentally by imaging the beams at points across the focal plane in an astigmatic system using a tilted lens. Mathematical analysis of the Gouy phase shows good agreement with the phase structure obtained in the experimental images. The polarization structure of the vector beam and the orbital angular momentum of the vortex beam are shown to be preserved.
Scientific Reports
Higher orders of orbital angular momentum states (OAMs) of light have been produced with a double-pass configuration through a zero-order vortex half-wave retarder (VHWR). This double-pass technique can reduce the number of VHWR plates used, thus reducing costs. The OAM states of the vortex beams are identified by the near-field Talbot effect. Polarization dependence of the vortex states can also be demonstrated with this VHWR using Talbot effect. Without using the Talbot patterns, this effect of the polarization on the vortex beam can not be recognized. A theoretical validation has also been provided to complement the experimental results. Our study gives an improved understanding of this approach to use a VHWR plate.
Polarization of orbital angular momentum carrying laser beams
Journal of the Optical Society of America A, 2013
Polarization of orbital angular momentum (OAM) carrying Laguerre-Gauss optical vortex beams, consistent with Maxwell's equations, is discussed, and experimental evidence for it is presented. The experiments reveal several novel features of such beams, including OAM dependent reconstruction of polarization and spatial profile during propagation.
Generating and measuring nondiffracting vector Bessel beams
Optics Letters, 2013
Nondiffracting vector Bessel beams are of considerable interest due to their nondiffracting nature and unique high-numerical-aperture focusing properties. Here we demonstrate their creation by a simple procedure requiring only a spatial light modulator and an azimuthally varying birefringent plate, known as a q-plate. We extend our control of both the geometric and dynamic phases to perform a polarization and modal decomposition on the vector field. We study both single-charged Bessel beams as well as superpositions and find good agreement with theory. Since we are able to encode nondiffracting modes with circular polarizations possessing different orbital angular momenta, we suggest these modes will be of interest in optical trapping, microscopy, and optical communication.
Generation of composite vortex beams by independent Spatial Light Modulator pixel addressing
2019
The composite optical beams being a result of superposition, are a promising way to study the orbital angular momentum and its effects. Their wide range of applications makes them attractive and easily available due to the growing interest in the Spatial Light Modulators (SLM). In this paper, we present a simple method for generating composite vortex patterns with high symmetry. Our method is simple, flexible and gives perfectly aligned beams, insensitive to mechanical vibrations. This method is based on the ability to split SLM cells between phase patterns that are to be superposed. This approach allows control of the intensity relation between those structures, enables their rotation and is capable to superpose more than two such structures. In this paper, we examine its ability to produce superposition of two optical vortices by presenting both theoretical and experimental results.
Spatiotemporal vortex beams and angular momentum
We present a space-time generalization of the known spatial (monochromatic) wave vortex beams carrying intrinsic orbital angular momentum (OAM) along the propagation direction. Generic spatio-temporal vortex beams are polychromatic and can carry intrinsic OAM at an arbitrary angle to the mean momentum. Applying either (i) a transverse wave-vector shift or (ii) a Lorentz boost to a monochromatic Bessel beam, we construct a family of either (i) time-diffracting or (ii) non-diffracting spatio-temporal Bessel beams, which are exact solutions of the Klein-Gordon wave equations. The proposed spatio-temporal OAM states are able to describe either photon or electron vortex states (both relativistic and nonrelativistic), and can find applications in particle collisions, optics of moving media, quantum communications, and astrophysics.
Optical vortex production mediated by azimuthal index of radial polarization
Journal of Optics, 2020
Special light beams are becoming more and more interesting due to their applications in particle manipulation, micromachining, telecommunications or light matter-interaction. Both spin and orbital angular momenta of light are exploited often in combination with spatially varying linear polarization profiles (e.g. radial or azimuthal distributions). In this work we study the interaction between those polarization profiles and the spin-orbit angular momenta, finding the relation involved in the mode coupling. We find that this manipulation can be used for in-line production of collinear optical vortices with different topological charges, which can be filtered or combined with controlled linear polarization. The results are valid for continuous wave and ultrashort pulses, as well as for collimated and focused beams. We theoretically demonstrate the proposal, which is further confirmed with numerical simulations and experimental measurements with ultrashort laser pulses.
Free-space realization of tunable pin-like optical vortex beams
Photonics Research, 2021
We demonstrate, both analytically and experimentally, free-space pin-like optical vortex beams (POVBs). Such angular-momentum-carrying beams feature tunable peak intensity and undergo robust antidiffracting propagation, realized by judiciously modulating both the amplitude and the phase profile of a standard laser beam. Specifically, they are generated by superimposing a radially symmetric power-law phase on a helical phase structure, which allows the inclusion of an orbital angular momentum term to the POVBs. During propagation in free space, these POVBs initially exhibit autofocusing dynamics, and subsequently their amplitude patterns morph into a high-order Bessel-like profile characterized by a hollow core and an annular main lobe with a constant or tunable width during propagation. In contrast with numerous previous endeavors on Bessel beams, our work represents the first demonstration of long-distance free-space generation of optical vortex “pins” with their peak intensity evo...
Observation of the vortex structure of a non-integer vortex beam
New Journal of Physics, 2004
An optical beam with an e ilφ phase structure carries an orbital angular momentum of lh per photon. For integer l values, the phase fronts of such beams form perfect helices with a single screw-phase dislocation, or vortex, on the beam axis. For non-integer l values, Berry (2004 J. Opt. A: Pure Appl. Opt. 6 259) predicts a complex-phase structure comprising many vortices at differing positions within the beam cross-section. Using a spatial light modulator we produce e ilφ beams with varying l. We examine the phase structure of such beams after propagation through an interference-based phase-measurement technique. As predicted, we observe that for half-integer l values, a line of alternating charge vortices is formed near the radial dislocation.
Geometric Phase and Intensity-Controlled Extrinsic Orbital Angular Momentum of Off-Axis Vortex Beams
Physical Review Applied, 2019
Off-axis vortex beams are generated by superposing a Gaussian beam onto a symmetric optical vortex beam of unit topological charge in a single-path interferometer with a control of their relative intensities and phases. The radial displacement of the point vortex from the center of the beam is controlled by varying the relative intensity of the superposed beams, while the azimuthal displacement of the vortex is controlled by the phase difference between the superposed beams. This phase difference is employed through the Pancharatnam-Berry geometric phase by different cyclic evolutions of the polarization states of the superposed beams on the Poincaré sphere. Interferometric field reconstruction of the resultant beams from experiment, simulation, and numerical calculations are used to obtain the transverse linear momentum density. The net transverse linear momentum vector and the resulting extrinsic orbital angular momentum in an off-axis vortex beam is demonstrated to be related to the radial and azimuthal position of the vortex across the beam. Controlling the Pancharatnam-Berry geometric phase and intensity ratio of the component beams is thus proposed as an effective and robust technique to tune the extrinsic orbital angular momentum of off-axis vortex beams. The presented results can be useful in applications ranging from optical manipulation of trapped microparticles, controlling micromachines using light with orbital angular momentum to enabling more flexibility in superresolution microscopy and controlled asymmetric interaction of light with atom, molecule, and Bose-Einstein condensate.