1,472 research outputs found
Light propagation in a birefringent plates with topological charge
We calculated the Fresnel paraxial propagator in a birefringent plate having
topological charge at its center, named "-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 "-plate" can be found for
many important specific input beam profiles. We paid particular attention to
the plate having a topological unit charge and we 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.Comment: 3 pages and 3 figures. Optics Letters styl
Resilience of orbital angular momentum qubits and effects on hybrid entanglement
The orbital angular momentum of light (OAM) provides a promising approach for
the implementation of multidimensional states (qudits) for quantum information
purposes. In order to characterize the degradation undergone by the information
content of qubits encoded in a bidimensional subspace of the orbital angular
momentum degree of freedom of photons, we study how the state fidelity is
affected by a transverse obstruction placed along the propagation direction of
the light beam. Emphasis is placed on the effects of planar and radial
hard-edged aperture functions on the state fidelity of Laguerre-Gaussian
transverse modes and the entanglement properties of polarization-OAM
hybrid-entangled photon pairs.Comment: 6 pages, 9 figure
Modelling Processes for Flexible Packaging
The paper explains that progress in flexible packaging technology can benefit from detailed modeling of processes and/or material properties. The example of film blowing is developed in some detail in view of its simplicity. It is shown that useful information on the molecular orientation in the produced film can be obtained by using the known values of the process variables, plus the outcome of a simple experiment that can be performed while the film is being produced, without disturbing the process. Molecular orientations are important in determining the film mechanical and barrier properties. Other examples are briefly discussed
Time-division multiplexing of the orbital angular momentum of light
We 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 -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 dividing different
input OAM states into different time-bins. The latter application provides a
simple approach to digital spiral spectroscopy of pulsed light.Comment: 3 pages and 2 figure
Electromagnetic confinement via spin-orbit interaction in anisotropic dielectrics
We investigate electromagnetic propagation in uniaxial dielectrics with a
transversely varying orientation of the optic axis, the latter staying
orthogonal everywhere to the propagation direction. In such a geometry, the
field experiences no refractive index gradients, yet it acquires a
transversely-modulated Pancharatnam-Berry phase, that is, a geometric phase
originating from a spin-orbit interaction. We show that the periodic evolution
of the geometric phase versus propagation gives rise to a
longitudinally-invariant effective potential. In certain configurations, this
geometric phase can provide transverse confinement and waveguiding. The
theoretical findings are tested and validated against numerical simulations of
the complete Maxwell's equations. Our results introduce and illustrate the role
of geometric phases on electromagnetic propagation over distances well
exceeding the diffraction length, paving the way to a whole new family of
guided waves and waveguides which do not rely on refractive index tailoring.Comment: 16 pages, 4 figure
Experimental generation and characterization of single-photon hybrid ququarts based on polarization-orbital angular momentum encoding
High-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 momentum of a single photon. Our novel technique, based on the
q-plate device, allows to prepare and measure the ququart in all five mutually
unbiased bases. We report the reconstruction of the four dimensional density
matrix through the tomographic procedure for different ququart states.Comment: 7 pages, 5 figure
Efficient generation and control of different order orbital angular momentum states for communication links
We present a novel optical device to encode and decode two bits of
information into different Orbital Angular Momentum (OAM) states of a paraxial
optical beam. Our device generates the four angular momentum states of order
and by Spin-To-Orbital angular momentum Conversion (STOC) in a
triangular optical loop arrangement. The switching among the four OAM states is
obtained by changing the polarization state of the circulating beam by two
quarter wave plates and the two-bit information is transferred to the beam OAM
exploiting a single -plate. The polarization of the exit beam is left free
for additional one bit of information. The transmission bandwidth of the device
may be as large as several megahertz if electro-optical switches are used to
change the beam polarization. This may be particularly useful in communication
system based on light OAM.Comment: 5 pages, 5 figures, 1 table. Submitte
Photon spin-to-orbital angular momentum conversion via an electrically tunable -plate
Exploiting electro-optic effects in liquid crystals, we achieved real-time
control of the retardation of liquid- crystal-based -plates through an
externally applied voltage. The newly conceived electro-optic -plates can be
operated as electrically driven converters of photon spin into orbital angular
momentum, enabling a variation of the orbital angular momentum probabilities of
the output photons over a time scale of milliseconds.Comment: 4 pages, 5 figures, submitte
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