Nonlinear conversion of photon spin to photon orbital angular momentum (original) (raw)
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Photon orbital angular momentum in a plasma vortex
We study theoretically the exchange of angular momentum between a photon beam and a plasma vortex, and demonstrate the possible excitation of photon angular momentum states in a plasma. This can be relevant to laboratory and space plasma diagnostics; radio astronomy self-calibration; and generating photon angular momentum beams. A static plasma perturbation with helical structure, and a rotating plasma vortex are studied in detail and a comparison between these two cases, and their relevance to the physical nature of photon OAM, is established. PACS numbers: 52.35.We,52.70.Gw,42.50.Tx,41.20.Jb It is well known that photons can carry not only intrinsic spin angular momentum (SAM), which is associated with their polarization state, but also extrinsic orbital angular momentum (OAM) . The existence of photon angular momentum has always been recognized on theoretical grounds, and was first experimentally demonstrated in the 1930's . While the experimental results led to quite some discussions about their proper interpretation [3], they did not excite much curiosity at the time as to their utilization. It is also known that quantum OAM states are associated with spherical wave functions , and can be excited by pointlike sources. Only recently photon OAM started receiving considerable attention, when it was found that they can be associated not only with spherical waves but also with cylindrical waves that can be easily produced by laser sources.
Photon orbital angular momentum: problems and perspectives
Fortschritte der Physik, 2004
The availability of laser beams carrying orbital angular momentum in addition to spin angular momentum paved the way to the observation of novel effects in quantum and classical optics. These effects are reviewed in this paper with emphasis on future perspectives.
Orbital angular momentum in the light emitted from laser-plasma accelerators
Characterizing the angular momentum carried by photons provides a new method of understanding the nature of laser-plasma interactions, beam-plasma interactions or beam propagation in an undulator. The recent results from experiments and simulations have shown that a plasma accelerator may be a promising source of ultrashort x-ray pulses with orbital angular momentum. However, the broadband and ultrashort nature of such a pulse makes it very challenging to measure the angular momentum properties of the photons. In this study, we review and discuss several potential methods for measurement of the orbital angular momentum from laser plasma accelerators.
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.
Sensors
We discuss interesting effects that occur when strongly focusing light with mth-order cylindrical–circular polarization. This type of hybrid polarization combines properties of the mth-order cylindrical polarization and circular polarization. Reluing on the Richards-Wolf formalism, we deduce analytical expressions that describe E- and H-vector components, intensity patterns, and projections of the Poynting vector and spin angular momentum (SAM) vector at the strong focus. The intensity of light in the strong focus is theoretically and numerically shown to have an even number of local maxima located along a closed contour centered at an on-axis point of zero intensity. We show that light generates 4m vortices of a transverse energy flow, with their centers located between the local intensity maxima. The transverse energy flow is also shown to change its handedness an even number of times proportional to the order of the optical vortex via a full circle around the optical axis. It is ...
Nonlinear relativistic electron Thomson Scattering for laser radiation with orbital angular momentum
Journal of Physics Communications, 2020
The classical nonlinear incoherent Thomson Scattering (TS) power spectrum from free relativistic electrons moving in a laser beam with orbital angular momentum (OAM) is investigated. The main focus in this paper is on the TS process as a diagnostic technique for this type of beams. Linearly polarized incoming radiation and electrons of very low initial kinetic energy are considered. Averaged spectra from electrons randomly covering the transverse laser pattern have different shape in the case of a beam with OAM as compared with the TEM00 case (with vanishing net OAM). Hence, spectrally resolved measurements are needed to discriminate between both cases. If electrons are distributed over the laser spot as thin stripes at a given angle with respect to the polarization direction, computations show non-trivial angular dependencies of integrated power of a laser with OAM as compared with the TEM00 mode. An experimental test of the OAM state of a laser beam is proposed based on these resu...
Nature Photonics, 2018
Optical interactions are governed by both spin and angular momentum conservation laws, which serve as a tool for controlling light-matter interactions or elucidating electron dynamics and structure of complex systems. Here, we uncover a form of simultaneous spin and orbital angular momentum conservation and show, theoretically and experimentally, that this phenomenon allows for unprecedented control over the divergence and polarization of extreme-ultraviolet vortex beams. High harmonics with spin and orbital angular momenta are produced, opening a novel regime of angular momentum conservation that allows for manipulation of the polarization of attosecond pulses-from linear to circular-and for the generation of circularly polarized vortices with tailored orbital angular momentum, including harmonic vortices with the same topological charge as the driving laser beam. Our work paves the way to ultrafast studies of chiral systems using high-harmonic beams with designer spin and orbital angular momentum.
Relativistic Electron Vortex Beams: Angular Momentum and Spin-Orbit Interaction
2011
Motivated by the recent discovery of electron vortex beams carrying orbital angular momentum (AM), we construct exact Bessel-beam solutions of the Dirac equation. They describe relativistic and nonparaxial corrections to the scalar electron beams. We describe the spin and orbital AM of the electron with Berry-phase corrections and predict the intrinsic spin-orbit coupling in free space. This can be observed as a spin-dependent probability distribution of the focused electron vortex beams. Moreover, the magnetic moment is calculated, which shows different g-factors for spin and orbital AM and also contains the Berry-phase correction.