1,721,110 research outputs found
Radial coherent and intelligent states of paraxial wave equation
No full textLadder operators for the radial index of the paraxial optical modes in the cylindrical coordinates are calculated. The operators obey the su(1,1) algebra commutation relations. Based on this Lie algebra, we found that coherent modes constructed as eigenstates of the destruction operator or resulting from the action of the displacement operator on the fundamental mode are different. Some properties of these two kinds of radial coherent modes are studied in detail
Spin-to-Orbital Angular Momentum Conversion and Spin Polarization Filtering in Electron Beams
No full textWe propose the design of a space-variantWien filter for electron beams that induces a spin half-turn and converts the corresponding spin angular momentum variation into orbital angular momentum of the beam itself by exploiting a geometrical phase arising in the spin manipulation. When applied to a spatially
coherent input spin-polarized electron beam, such a device can generate an electron vortex beam, carrying orbital angular momentum. When applied to an unpolarized input beam, the proposed device, in combination with a suitable diffraction element, can act as a very effective spin-polarization filter. The
same approach can also be applied to neutron or atom beams
Light propagation in a birefringent plate with topological charge
No full textWe calculated the Fresnel paraxial propagator in a birefringent plate having topological charge q at its center, named “q-plate.” We studied the change of the beam transverse profile when it traverses the plate. An analytical closed form of the beam profile propagating in the q-plate can be found for many important specific input beam profiles. We paid particular attention to the plate having a topological unit charge and found that if small losses due to reflection, absorption, and scattering are neglected, the plate can convert the photon spin into orbital angular momentum with up to 100% efficiency provided the thickness of the plate is less than the Rayleigh range of the incident beam
Convertitore di momento orbitale in momento di spin per la polarizzazione di fasci di particelle
No full textSistema per la generazione di fasci elettronici a vortice, partendo da fasci polarizzati di spin, ovvero per la generazione di fasci polarizzati di spin, partendo da fasci elettronici a vortice. Questi ultimi possono essere generati mediante tecniche olografiche recentemente introdotte
Hypergeometric-Gaussian modes
No full textWe studied a novel family of paraxial laser beams forming an overcomplete yet nonorthogonal set of modes. These modes have a singular phase profile and are eigenfunctions of the photon orbital angular momentum. The intensity profile is characterized by a single brilliant ring with the singularity at its center, where the field amplitude vanishes. The complex amplitude is proportional to the degenerate (confluent) hypergeometric function, and therefore we term such beams hypergeometric-Gaussian (HyGG) modes. Unlike the recently introduced hypergeometric modes [Opt. Lett. 32, 742 (2007)], the HyGG modes carry a finite power and have been generated in this work with a liquid-crystal spatial light modulator. We briefly consider some subfamilies of the HyGG modes as the modified Bessel Gaussian modes, the modified exponential Gaussian modes, and the modified Laguerre-Gaussian modes
Time-division multiplexing of the orbital angular momentum of light
No full textWe present an optical setup for generating a sequence of light pulses in which the orbital angular momentum (OAM) degree of freedom is correlated with the temporal one. The setup is based on a single q plate within a ring optical resonator. By this approach, we demonstrate the generation of a train of pulses carrying increasing values of OAM, or, alternatively, of a controlled temporal sequence of pulses having prescribed OAM superposition states. Finally, we exhibit an “OAM-to-time conversion” apparatus that divides different input OAM states into different time bins. The latter application provides a simple approach to digital spiral spectroscopy of pulsed light. © 2012 Optical
Society of Americ
Polarization-controlled evolution of light transverse modes and associated Pancharatnam geometric phase in orbital angular momentum
No full textWe present an easy, efficient, and fast method to generate arbitrary linear combinations of light orbital
angular-momentum eigenstates l = ±2 starting from a linearly polarized TEM00 laser beam. The method exploits
the spin-to-orbital angular-momentum co
Improved focusing with Hypergeometric-Gaussian type-II optical modes
No full textWe present a novel family of paraxial optical beams having a confluent hypergeometric transverse profile, which we name hypergeometric Gauss modes of type-II (HyGG-II). These modes are eigenmodes of the photon orbital angular momentum and they have the l
Universal unitary gate for single-photon spinorbit two-qubit states
No full textThe recently demonstrated possibility of entangling opposite values of the orbital angular momentum (OAM) of a photon with its spin enables the realization of nontrivial one-photon spin-orbit four-dimensional states for quantum information purposes. Hitherto, however, an optical device that can able to perform arbitrary unitary transformations on such spin-orbit photon states has not been proposed yet. In this work we show how to realize such a "universal unitary gate" device, based only on the existing optical technology, and describe its operation. Besides the quantum information field, the proposed device may find applications wherever an efficient and convenient manipulation of the combined OAM and spin of light is required.Full Tex
Efficient generation and sorting of orbital angular momentum eigenmodes of light by thermally tuned q-plates
No full textWe present methods for generating and for sorting specific orbital angular momentum (OAM) eigenmodes of a light beam with high efficiency, using a liquid crystal birefringent plate with unit topological charge known as “q-plate.” The generation efficiency has been optimized by tuning the optical retardation of the q-plate with temperature. The measured OAM m=2 eigenmodes generation efficiency from an input TEM00 beam was of 97%. Mode sorting of the two input OAM m=2 eigenmodes was achieved with an efficiency of 81%
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