Search results for "Core"
showing 10 items of 1999 documents
Seeded intermodal four-wave mixing in a highly multimode fiber
2018
International audience; We experimentally and theoretically investigate the process of seeded intermodal four-wave mixing in a graded-index multimode fiber, pumped in the normal dispersion regime. By using a fiber with a 100-mu m core diameter, we generate a parametric sideband in the C-band (1530-1565 nm), hence allowing the use of an erbium-based laser to seed the mixing process. To limit nonlinear coupling between the pump and the seed to low-order fiber modes, the waist diameter of the pump beam is properly adjusted. We observe that the superimposed seed stimulates the generation of new spectral sidebands. A detailed characterization of the spectral and spatial properties of these sideb…
Low loss microstructured chalcogenide fibers for large non linear effects at 1995 nm
2010
International audience; Microstructured optical fibers (MOFs) are traditionally prepared using the stack and draw technique. In order to avoid the interfaces problems observed in chalcogenide glasses, we have developed a new casting method to prepare the chalcogenide preform. This method allows to reach optical losses around 0.4 dB/m at 1.55 µm and less than 0.05 dB/m in the mid IR. Various As(38)Se(62) chalcogenide microstructured fibers have been prepared in order to combine large non linear index of these glasses with the mode control offered by MOF structures. Small core fibers have been drawn to enhance the non linearities. In one of these, three Stokes order have been generated by Ram…
Characterization of optogeometric parameters of optical fibers by near-field scanning probe microscopies
2000
The combination of atomic-force and scanning-near-field optical microscopies is useful for characterizing the physical and optical parameters of optoelectronic devices. With a commercial atomic-force microscope adapted to perform scanning-near-field optical measurements, we succeed in determining core diameters, localizing the erbium doping zone, and analyzing propagation modes in erbium-doped and multimodal optical fibers.
In-Fiber Acousto-Optics for the Broadband Measurement of the UV-Induced Refractive Index Change in Photosensitive Fibers
2019
In fiber acousto-optics has been demonstrated to be a versatile, highly sensitive technique that allows characterizing different parameters of singlemode or few-mode fibers, such as dispersion curves, radius or core refractive index, in a broadband wavelength range. The working principle of the technique relies in the fact that a variation in a parameter of the fiber leads to a shift in the optical wavelength that fulfills the acousto-optic phase matching condition. Thus, by measuring this wavelength shift it is possible to evaluate the change in the parameter under study. The technique shows a low detection limit: for example, it is as low as 10-8 for the core refractive index, in singlemo…
Fourth-order cascaded Raman shift in AsSe chalcogenide suspended-core fiber pumped at 2 μm
2011
International audience; Cascaded Raman wavelength shifting up to the fourth order ranging from 2092 to 2450nm is demonstrated using a nanosecond pump at 1995nm in a low-loss As38Se62 suspended-core microstructured fiber. These four Stokes shifts are obtained with a low peak power of 11W, and only 3W are required to obtain three shifts. The Raman gain coefficient for the fiber is estimated to (1.6 +-0.5)x 10e−11 m/W at 1995nm. The positions and the amplitudes of the Raman peaks are well reproduced by the numerical simulations of the nonlinear propagation.
Ellipsoidal core-shell cylindrical microphases in PS-b -PB-b -PCL triblock copolymers with a crystallizable matrix
1997
Polystyrene-block-polybutadiene-block-poly(e-caprolactone) SBC triblock copolymers with a PCL matrix exhibit microphase separation into three different phases within the spherulitic superstructures. Mixing of the PS-block can occur upon melting of the PCL-block if the molecular weight is low enough. Even though the crystallization takes place well below the PS-glass transition, a deformation of the amorphous microphases into ellipsoidal core-shell cylindrical microdomains is observed by TEM. These copolymers have mechanical properties which are dominated by the PCL (Poly(e-caprolactone)) matrix with an influence of the amorphous blocks.
Applications of spray-drying in microencapsulation of food ingredients: An overview
2007
International audience; Spray-drying process has been used for decades to encapsulate food ingredients such as flavors, lipids, and carotenoids. During this drying process, the evaporation of solvent, that is most often water, is rapid and the entrapment of the interest compound occurs quasi-instantaneously. This required property imposes a strict screening of the encapsulating materials to be used in addition to an optimization of the operating conditions. Likewise, if the encapsulated compound is of hydrophobic nature, the stability of the feed emulsion before drying should also be considered. Thus, spray-drying microencapsulation process must rather be considered as an art than a science…
Effect of Fiber-Reinforced Composite and Elastic Post on the Fracture Resistance of Premolars with Root Canal Treatment—An In Vitro Pilot Study
2020
(1) Background: To analyze the fracture resistance of endodontically upper premolar teeth restored with glass fiber reinforced posts, glass fiber elastic posts, conventional composite resin (CR) and glass fiber reinforced composite (FRC) resins as restorations. (2) Methods: Seventy premolars were submitted to root canal treatment and restored with the following restorative materials (n = 10): A. FRC posts restored with resin
Luminescent silicon nanocrystals produced by near-infrared nanosecond pulsed laser ablation in water
2014
Abstract We report the investigation of luminescent nanoparticles produced by ns pulsed Nd:YAG laser ablation of silicon in water. Combined characterization by AFM and IR techniques proves that these nanoparticles have a mean size of ∼3 nm and a core–shell structure consisting of a Si-nanocrystal surrounded by an oxide layer. Time resolved luminescence spectra evidence visible and UV emissions; a band around 1.9 eV originates from Si-nanocrystals, while two bands centered at 2.7 eV and 4.4 eV are associated with oxygen deficient centers in the SiO 2 shell.
Improvement of IPMSM performance through a mixed radial-tangential rotor structure
2010
In this paper an IPMSM (Interior Permanent Magnet Synchronous Motor) rotor configuration optimization is proposed in order to increase the performances in terms of torque, limiting at the same time the rotor leakage flux. The final mixed radial and tangential rotor configuration here proposed and described determines a reduction in PM material quantity of about 25% compared to a tangential IPMSM one with the same dimension and weight, together with an increase of the motoring torque of about 50%. Some simulation carried out by using a FEM software and a comparative analysis with two traditional IPMSMs rotor configurations show that a significant improvement can be achieved with limited chan…