Low-mode Optical Fibers Research Articles

Magnetic Speckle-Pattern Rotation in Gyrotropic Low-Mode Optical Fiber Coated by Conductive Nanoshell

We have investigated theoretically the possibility of control of magnetic speckle-pattern rotation in gyrotropic optical fiber coated by conductive nanoshell. Investigation has been carried out for graphene and silver coated fibers. In graphene-coated fiber speckle-pattern rotation may be tuned by both magnetic field and chemical potential of graphene. It is shown that fiber coating by conductive nanoshell may leads to suppression of magnetic speckle-pattern rotation even for low-gyrotropic quartz fiber.

Using tunable lasers for photochromic coherent speckle diagnostics of bulk scattering media and optical fibers

We have observed for the first time the dynamics of a speckle field generated in bulk scattering partly ordered media or low-mode optical fibers probed by a laser diode (λ=654 nm) and a compact diode-pumped YAG:Nd laser (λ=532 μm) in the regime of frequency tuning. The dynamic coherent speckle-photo-chromic effect can be observed provided that the deviation of the probing radiation frequency is comparable with or greater than the effective phase delay difference between modes in the optical fiber or between waves in the random scattering medium. Using the proposed photochromic speckle technique, it is possible to determine the intermode dispersion of fibers with a length on the order of one meter and the dispersion of phase delay in test fluoroplastic structures in the regimes of severalfold scattering (for a sample thickness of 10–20 μm) or multiple scattering (for a thickness of up to ∼2 cm).

Rotation of the speckle pattern in a low-mode optical fiber in a longitudinal magnetic field

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text L. I. Ardasheva, M. O. Sadykova, N. R. Sadykov, and V. E. Chernyakov, "Rotation of the speckle pattern in a low-mode optical fiber in a longitudinal magnetic field," J. Opt. Technol. 69, 451- (2002) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

Optical vortices in low-mode fibers: III. Dislocation reactions, phase transitions, and topological birefringence

Topological birefringence of waves in optical fibers resulting from the spin-orbit interaction in the field of optical vortices is manifested, as a rule, in the form of Rytov-Magnus unified optical effect. At the same time, the field transformations caused by this effect are not explicitly related to the evolution of phase dislocations of longitudinal and transverse components of the electric and the magnetic fields. This relation can be provided by the dislocation reactions proposed by Berry. As opposed to the Berry’s approach, where dislocation reactions at the wavefront surface are considered, it is suggested in this work that topological reactions at the specific characteristic surface of the wave field formed by the coordinate representation of the transverse components of the Poynting vector be considered. Using the action of topological birefringence in a low-mode optical fiber as an example, it is shown that the course of a topological reaction in a vector optical field is accompanied by rigorous conservation of the total topological index of the characteristic surface and does not depend on the presence of an interface (where topological charges can originate and annihilate). The total topological index of a dislocation reaction is found to be equal to the absolute value of the sum of the topological charge and the spirality of the vector wave field.

Connection between spatial coherence and modal structure in optical fibers and semiconductor lasers

The evaluation of the relative amplitudes of the modes of a guiding structure is not easy when the relative amplitudes of the modes are very different among themselves. In this paper we show how a measurement of the modulus of the complex degree of spatial coherence on the exit face of a passive or active guiding structure, supporting a small number of guided modes, allows us to determine the model content of the propagating field. Experimental results obtained performing measurements on a low-mode optical fiber and a stripe DH laser are also presented.