Twisted photons (original) (raw)
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On the exchange of orbital angular momentum between twisted photons and atomic electrons
We obtain an expression for the matrix element for a twisted (Laguerre-Gaussian profile) photon scattering from a hydrogen atom. We consider photons incoming with an orbital angular momentum (OAM) of ℓ , carried by a factor of e iℓφ not present in a plane-wave or pure Gaussian profile beam. The nature of the transfer of +2ℓ units of OAM from the photon to the azimuthal atomic quantum number of the atom is investigated. We obtain simple formulae for these OAM flip transitions for elastic forward scattering of twisted photons when the photon wavelength λ is large compared with the atomic target size a, and small compared the Rayleigh range z R , which characterizes the collimation length of the twisted photon beam.
On Exchange of Orbital Angular Momentum Between Twisted Photons and Atomic Electrons
2012
We obtain an expression for the matrix element for a twisted (Laguerre-Gaussian profile) photon scattering from a hydrogen atom. We consider photons incoming with an orbital angular momentum (OAM) of ℓħ, carried by a factor of e^i ℓϕ not present in a plane-wave or pure Gaussian profile beam. The nature of the transfer of +2ℓ units of OAM from the photon to the azimuthal atomic quantum number of the atom is investigated. We obtain simple formulae for these OAM flip transitions for elastic forward scattering of twisted photons when the photon wavelength λ is large compared with the atomic target size a, and small compared the Rayleigh range z_R, which characterizes the collimation length of the twisted photon beam.
Quantum Information Transfer from Spin to Orbital Angular Momentum of Photons
Physical Review Letters, 2009
The optical "spin-orbit" coupling occurring in a suitably patterned nonuniform birefringent plate known as 'q-plate' allows entangling the polarization of a single photon with its orbital angular momentum (OAM). This process, in turn, can be exploited for building a bidirectional "spin-OAM interface", capable of transposing the quantum information from the spin to the OAM degree of freedom of photons and vice versa. Here, we experimentally demonstrate this process by singlephoton quantum tomographic analysis. Moreover, we show that two-photon quantum correlations such as those resulting from coalescence interference can be successfully transferred into the OAM degree of freedom.
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.
Journal of Optics, 2011
A few years ago the possibility of coupling and inter-converting the spin and orbital angular momentum (SAM and OAM) of paraxial light beams in inhomogeneous anisotropic media was demonstrated. An important case is provided by waveplates having a singular transverse pattern of the birefringent optical axis, with a topological singularity of charge q at the plate center, hence named 'q-plates'. The introduction of q-plates has given rise in recent years to a number of new results and to significant progress in the field of orbital angular momentum of light. Particularly promising are the quantum photonic applications, because the polarization control of OAM allows the transfer of quantum information from the SAM qubit space to an OAM subspace of a photon and vice versa. In this paper, we review the development of the q-plate idea and some of the most significant results that have originated from it, and we will briefly touch on many other related findings concerning the interaction of the SAM and OAM of light.
Optical orbital angular momentum: twisted light and chirality
Optics letters, 2018
The question of how the orbital angular momentum of structured light might engage with chiral matter is a topic of resurgent interest. By taking account of electric quadrupole transition moments, it is shown that the handedness of the beam can indeed be exhibited in local chiral effects, being dependent on the sign of the topological charge. In the specific case of absorption, a significant interplay of wavefront structure and polarization is resolved, and clear differences in behavior are identified for systems possessing a degree of orientational order and for those that are randomly oriented.
Orbital Angular Momentum Exchange in the Interaction of Twisted Light with Molecules
Physical Review Letters, 2002
In the interaction of molecules with light endowed with orbital angular momentum, an exchange of orbital angular momentum in an electric dipole transition occurs only between the light and the center of mass motion; i.e., internal ''electronic-type'' motion does not participate in any exchange of orbital angular momentum in a dipole transition. A quadrupole transition is the lowest electric multipolar process in which an exchange of orbital angular momentum can occur between the light, the internal motion, and the center of mass motion. This rules out experiments seeking to observe exchange of orbital angular momentum between light beams and the internal motion in electric dipole transitions.
Quantum interference by coherence transfer from spin to orbital angular momentum of photons
2009
The orbital angular momentum carried by single photons represents a promising resource in the quantum information field. In this paper we report the characterization in the quantum regime of a recently introduced optical device, known as q-plate. Exploiting the spin-orbit coupling that takes place in the q-plate, it is possible to transfer coherently the information from the polarization to the orbital angular momentum degree of freedom, and viceversa. Hence the q-plate provides a reliable bi-directional interface between polarization and orbital angular momentum. As a first paradigmatic demonstration of the q-plate properties, we have carried out the first experimental Hong-Ou-mandel effect purely observed in the orbital angular momentum degree of freedom.
On the Coupling of Photon Spin to Electron Orbital Angular Momentum
Partially gold coated 90° glass wedges and a semi-infinite slit in a thin film of gold ending in a conducting nano-junction serve as samples to investigate the transfer of photon spin to electron orbital angular momentum. These structures were specifically designed as samples where an incident beam of light is retroreflected. Since in the process of retroreflection the turning sense of a circularly polarized beam of light does not change and the direction of propagation is inverted, the photon spin is inverted. Due to conservation of angular momentum a transfer of photon spin to electron orbital angular momentum of conduction electrons occurs. In the structures a circular movement of electrons is blocked and therefore the transfered spin can be detected as a photovoltage due to an electromotive force which is induced by the transfer of angular momentum. Depending on the polarization of the incident beam, a maximum photovoltage of about 0,2µV was measured for both structures. The results are interpreted in terms of a classical electrodynamic model of the monochromatic linearly polarized photon as a propagating solitary electromagnetic wave of finite energy h which carries an angular momentum ℎ 2 which is elaborated elsewhere where h is Planck's constant and the frequency of light. The relative values of the measured photovoltages for different polarizations can well be explained by the electrodynamic model of a photon and an associated spin angular momentum. The absolute values of the measured photovoltages are also consistent with the interpretation. The observed effects are closely related to the lateral Fedorov Imbert shift of focused beams in optics and the optical spin Hall effect and to other non linear optical effects such as the inverse faraday effect for which a new interpretation is given here in terms of the electrodynamic model of the photon and its spin.
Polarization control of single photon quantum orbital angular momentum states
Optics Express, 2009
The orbital angular momentum of photons, being defined in an infinitely dimensional discrete Hilbert space, offers a promising resource for high-dimensional quantum information protocols in quantum optics. The biggest obstacle to its wider use is presently represented by the limited set of tools available for its control and manipulation. Here, we introduce and test experimentally a series of simple optical schemes for the coherent transfer of quantum information from the polarization to the orbital angular momentum of single photons and vice versa. All our schemes exploit a newly developed optical device, the so-called "q-plate", which enables the manipulation of the photon orbital angular momentum driven by the polarization degree of freedom. By stacking several qplates in a suitable sequence, one can also access to higher-order angular momentum subspaces. In particular, we demonstrate the control of the orbital angular momentum m degree of freedom within the subspaces of |m| = 2h and |m| = 4h per photon. Our experiments prove that these schemes are reliable, efficient and have a high fidelity.