1,720,991 research outputs found
Gouy phase shift in nondiffracting Bessel beams
No full textThe results of a theoretical and experimental investigation of the Gouy effect in Bessel beams are presented. We point out that the peculiar feature of the Bessel beams of being nondiffracting is related to the accumulation of an extra axial phase shift (i.e., the Gouy phase shift) linearly dependent on the propagation distance. The constant spatial rate of variation of the Gouy phase shift is independent of the order of the Bessel beam, while it is a growing function of the transverse component of the angular spectrum wave-vectors, originated by the transverse confinement of the beam. A free-space Mach-Zehnder interferometer has been set-up for measuring the transverse intensity distribution of the interference between holographically-produced finite-aperture Bessel beams of order from zero up to three and a reference Gaussian beam, at a wavelength of 633 nm. The interference patterns have been registered for different propagation distances and show a spatial periodicity, in agreement with the expected period due to the linear increase of the Gouy phase shift of the realized Bessel beams
Ottimizzazione dei parametri di filatura per la riduzione della birifrangenza nelle fibre ottiche
No full textMultiplazione a divisione di momento angolare orbitale con fasci di Bessel
No full textWe present an apparata for multiplexing and demultiplexing free-space nondiffracting Bessel beams of order from 0 to 3, carrying different values of orbital angular momentum at the wavelength of 633 nm
Drawing parameters optimization for birefringence reduction in optical fibers
No full textThe impact of the drawing process on the stress-induced birefringence in optical fiber is experimentally analyzed. By means of the photoelastic tomographic technique, residual internal stresses are measured in fiber samples drawn under different conditions of temperature, drawing tension and speed. From measured residual stress distributions, the stress-induced birefringence and beatlength are mathematically derived and compared, proving that an effective birefringence reduction can be obtained by a proper choice of drawing parameters
Local Birefringence in Unidirectionally Spun Fibers
No full textThe application of a spinning step in the drawing process is known to improve optical-fiber polarization mode dispersion. For a more comprehensive understanding of the mechanism through which spinning modifies fiber performances, in this paper, the authors investigate the effect of unidirectional spinning on local fiber birefringence in terms of the effectiveness of spin-function transfer and reduction of the local intrinsic birefringence under different drawing conditions. The actual frozen-in spin is experimentally recovered by means of a cut-back procedure. Different from the case of a periodic spinning, a unidirectional spinning correctly reproduces the nominally imparted spin rate in agreement with theoretical modelizations of the transfer effectiveness of the spinning process. A theoretical explanation for the experimental evidence, recently proved by tomographic stress measurements, of spinning affecting fiber linear intrinsic birefringence is provided. In particular, the interaction of drawing parameters and spinning process in defining stress development into fibers is considered. To validate the proposed model, further tomographic reconstructions of stress profiles in fiber spun at different rates and drawing speed were carried out. Besides, corresponding stress-induced birefringence values were estimated and compared with those recovered by the cut-back technique. Variations of spun fiber beatlength values with respect to the unspun case, as obtained from both measurement techniques, are in good agreement, providing a further reliable confirmation that an improvement of the beatlength may proceed as a consequence of the applied spi
Caratterizzazione tomografica della regione di cladding di una fibra ottica singolo modo standard per telecomnicazioni
No full textThe existence of two cladding zones, which present different optical properties is experimentally verified for the first time in standard single mode fiber by means of a high precision photoelastic tomographic fiber characterization
Photoelastic tomographic characterization of stress distribution in fibers in dependence of drawing parameters
No full textResidual stress distribution is experimentally analyzed in different optical fibers thanks to photoelastic tomography characterization to demonstrate the dependence by fiber drawing parameters, such as speed tension and temperature
- …
