2,954 research outputs found
Polarization and spatial information recovery by modal dispersal and phase conjugation: properties and applications
We describe recent theoretical and experimental studies of polarization and spatial information recovery by modal dispersal and phase conjugation. We discuss the fidelity of this phase-conjugation process as a function of input-beam launching conditions. We also describe several new applications of the scheme which involve correction of nonreciprocal polarization distortions, correction of lossy amplitude distortions, phase-conjugate multimode fiber-optic interferometers and gyros, temporal data channeling between beams, and all-optical beam thresholding
Wave-vector and polarization dependence of conical refraction
We experimentally address the wave-vector and polarization dependence of the
internal conical refraction phenomenon by demonstrating that an input light
beam of elliptical transverse profile refracts into two beams after passing
along one of the optic axes of a biaxial crystal, i.e. it exhibits double
refraction instead of refracting conically. Such double refraction is
investigated by the independent rotation of a linear polarizer and a
cylindrical lens. Expressions to describe the position and the intensity
pattern of the refracted beams are presented and applied to predict the
intensity pattern for an axicon beam propagating along the optic axis of a
biaxial crystal
Direct fiber vector eigenmode multiplexing transmission seeded by integrated optical vortex emitters
Spatial modes have received substantial attention over the last decades and are used in optical communication applications. In fiber-optic communications, the employed linearly polarized modes and phase vortex modes carrying orbital angular momentum can be synthesized by fiber vector eigenmodes. To improve the transmission capacity and miniaturize the communication system, straightforward fiber vector eigenmode multiplexing and generation of fiber-eigenmode-like polarization vortices (vector vortex modes) using photonic integrated devices are of substantial interest. Here, we propose and demonstrate direct fiber vector eigenmode multiplexing transmission seeded by integrated optical vortex emitters. By exploiting vector vortex modes (radially and azimuthally polarized beams) generated from silicon microring resonators etched with angular gratings, we report data-carrying fiber vector eigenmode multiplexing transmission through a 2-km large-core fiber, showing low-level mode crosstalk and favorable link performance. These demonstrations may open up added capacity scaling opportunities by directly accessing multiple vector eigenmodes in the fiber and provide compact solutions to replace bulky diffractive optical elements for generating various optical vector beams
Conical refraction healing after partially blocking the input beam
In conical refraction, when a focused Gaussian beam passes along one of the
optic axes of a biaxial crystal it is transformed into a pair of concentric
bright rings at the focal plane. We demonstrate both theoretically and
experimentally that this transformation is hardly affected by partially
blocking the Gaussian input beam with an obstacle. We analyze the influence of
the size of the obstruction both on the transverse intensity pattern of the
beam and on its state of polarization, which is shown to be very robust
Optical anisotropy induced by torsion stresses in LiNbO3 crystals: appearance of an optical vortex
We report the results of studies of torsion effect on the optical
birefringence in LiNbO3 crystals. We have found that twisting of those crystals
causes a birefringence distribution revealing non-trivial peculiarities. In
particular, it has a special point at the center of cross section perpendicular
to the torsion axis where zero birefringence value occurs. It has also been
ascertained that the surface of the spatial birefringence distribution has a
conical shape, with the cone axis coinciding with the torsion axis. We have
revealed that an optical vortex, with the topological charge equal to unity,
appears under the torsion of LiNbO3 crystals. It has been shown that, contrary
to the q-plate, both the efficiency of spin-orbital coupling and the orbital
momentum of the emergent light can be operated by the torque moment.Comment: 28 pages, 8 figure
Fiber optic sensor based on dual ring resonator system
A comprehensive study of fiber optic sensors based on a dual ring resonator system has been conducted. A new theoretical model is established for a single fiber optic ring resonator. The performance of fiber optic sensors based on the dual ring resonator system is then analyzed, based on this model. The best configuration for the dual ring resonator system is determined in terms of the shot-noise-limited minimum detectable phase change, as well as the environmental stability when polarization crosstalk is present. The relationship between the coherence length of semiconductor light sources and the resonator loop lengths is investigated, with the aim of eliminating phase noise effects. Moreover, the effect of length mismatch between the two resonator loops is discussed. Finally, the fundamental output characteristics of fiber optic sensors based on dual ring resonator system are verified experimentally. Some recommendations are also given for further possible improvement
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