1,721,947 research outputs found
Liquid crystal q-plates: classical and quantum photonic applications
No full textLiquid crystals (LC) are particularly well suited for the manipulation of the angular momentum of light. Only recently, the possibility of coupling the LCs and the so-called orbital angular momentum (OAM) of light has been identified. OAM is associated with a light beam having a helical wavefront and an optical vortex at its axis. A singular-patterned LC plate, named “q-plate”, can be used for generating and controlling helical beams of light, or “vortex beams”. The q- plate can be also used in the quantum regime, for controlling the OAM of single photons, leading to several applications in the quantum information field
Helical modes of light and optical spin-to-orbital angular momentum conversion in inhomogeneous liquid crystals: prospects for nonlinear optics
No full textPhotoinduced reorientation phenomena in dyed liquid crystals: recent steps toward a complete understanding of the underlying mechanism
No full textSpin and orbital angular momentum of light and particle beams and their inter-conversion
No full textPrimitive Chain Network Simulations of Entangled Melts of Symmetric and Asymmetric Star Polymers in Uniaxial Elongational Flows
No full textIanniruberto and Marrucci developed a theory whereby entangled branched
polymers behave like linear ones in fast elongational flows. In order to test
such prediction, Huang et al. performed elongational measurements on star
polymer melts, indeed revealing that, in fast flows, the elongational viscosity
is insensitive to the molecular structure, provided the molecular weight of the
backbone is the same. Inspired by these studies, we here report on results
obtained with multi-chain slip-link simulations for symmetric and asymmetric
star polymer melts, as well as calculations of the Rouse time of the examined
branched structures. The simulations semi-quantitatively reproduce the
experimental data if the Kuhn-segment orientation-induced reduction of friction
(SORF) is accounted for. The observed insensitivity of the nonlinear
elongational viscosity to the molecular structure for the same span molar mass
may be due to several factors. In the symmetric case, the calculated Rouse time
of the star marginally differs from that of the linear molecule, so that
possible differences in the observed stress fall within the experimental
uncertainty. Secondly, it is possible that the flow-induced formation of hooked
star pairs makes the effective Rouse time of the aggregate even closer to that
of the linear polymer because the friction center moves towards the branchpoint
of the star molecule. In the asymmetric case, it is shown that the stress
contributed by the short arms is negligible with respect to that of the long
ones. However, such stress-reduction is balanced by a dilution effect whereby
the unstretched arms reduce SORF as they decrease the Kuhn-segment order
parameter of the system. As a result of that dilution, the stress contributed
by the backbone is larger. The two effects compensate one another so that the
overall stress is virtually the same as the other architectures.Comment: 19 pages, 6 figure
Spin and orbital angular momentum coupling
No full textThe concepts of spin and orbital angular momentum of light and the phenomena leading to their interaction are reviewed here, with a focus on those aspects that are most relevant for optical communication. I introduce a classification of spin-orbit optical phenomena in two main categories: paraxial and non-paraxial effects. I then describe the theory of spin-orbit effects occurring for paraxial waves traveling through inhomogeneous birefringent media, such as for example q-plates or meta-surfaces. Next, among the various classes of non-paraxial spin-orbit effects, I focus on those falling under the name of “spin-Hall effect of light”, in particular on the role of these effects for the confined optical modes traveling in optical fibers. A range of potential applications of these spin-orbit optical phenomena for classical and quantum optical communication are finally reviewed
Rotating light with light: Generation of helical modes of light by spin-to-orbital angular momentum conversion in inhomogeneous liquid crystals
No full textQuantum optics: Spin gives direction
No full textLight emitted near an optical waveguide is captured and equally split into two modes with opposite directions of propagation. By controlling the dipole spin of the emitter, it is possible to break this symmetry and select only one direction
Experimental generation and characterization of single-photon hybrid ququarts based on polarization and orbital angular momentum encoding
No full textHigh-dimensional quantum states, or qudits, represent a promising resource in the quantum information field.
Here we present the experimental generation of four-dimensional quantum states, or ququarts, encoded in the polarization and orbital angular mome
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