Search results for "continuum"
showing 10 items of 477 documents
Multidimensional shaping of spatiotemporal waves in multimode nonlinear fibers
2019
Recent experiments have shown that nonlinear wave propagation in multimode optical fibers leads to complex spatio-temporal phenomena. In this talk, we introduce new approaches for the control and optimization of nonlinear beam reshaping in the spatial, temporal and spectral dimensions. The first approach applies to spatial beam self-cleaning the technique of transverse wavefront shaping, which permits to launch an optimized input mode combination, that results in the stable generation of a whole nonlinear mode alphabet at the fiber output. The second approach introduces a longitudinal tapering of the core diameter of multimode active and passive fibers, which permits to generate ultra-wideb…
Chalcogenide microstructured optical fibers : from linear to nonlinear properties
2010
International audience; In this talk, we review the linear properties of chalcogenide microstructured optical fibers (MOFs) of several types. We mainly focus our talk on mid-infrared applications of such fibers. We start with the general properties of solid core MOFs made of these high index glasses and compare them with the ones of silica. Then, we give some details concerning a solid core MOF made of TAS glass. Next, we describe the first guiding suspended chalcogenide MOF and explain how it was designed for supercontinuum generation in the mid-infrared. Both linear and nonlinear properties of As2S3 suspended core MOFs are also numerically studied. In the next part, We describe the design…
New theoretical and experimental concepts for frequency generation in optical fibers: modulation instability, pulsed Raman Laser and kinetic approach…
2009
Following a brief introduction to optical fibers, we combine the effect of modulational instability and Raman self-frequency shift to generate a frequency combs with a spectral width higher than 100 nm and a central frequency shifted towards higher wavelengths. Then, the stimulated Raman effect is used in a ring cavity coupled with nonlinear polarization rotation and polarization filtering. A pulsed regime is obtained at the wavelength of the first Stokes emission and presents a rich zoology of experimental dynamic pulsed regimes. A second main line of this manuscript considers the incoherent regime of supercontinuum generation. We show that under certain conditions, the spectral broadening…
Etude des sources supercontinuum à fibres transparentes dans le moyen infrarouge
2012
The work reported in this thesis deals with the study of the supercontinuum generation in fibers transparent in the mid-infrared. To generate a supercontinuum between 3 and 5 µm we compare different glass families such as fluoride glasses, tellurite glasses and chalcogenide glasses. These fibers are pumped with fiber lasers emitting at 2 µm with nanosecond or picosecond pulse duration. This wavelength allows us to reach the zero dispersion wavelength of the chalcogenide tapered fibers. We report supercontinuum generation up to 3800 nm in a fluoride glass fiber. A connection with 75 % of transmission is made between a ZBLAN and a SiO2 fiber. We also measured absorption lines of the methane a…
VLBA polarimetric monitoring of 3C 111
2018
Context. While studies of large samples of jets of active galactic nuclei (AGN) are important in order to establish a global picture, dedicated single-source studies are an invaluable tool for probing crucial processes within jets on parsec scales. These processes involve in particular the formation and geometry of the jet magnetic field as well as the flow itself. Aims. We aim to better understand the dynamics within relativistic magneto-hydrodynamical flows in the extreme environment and close vicinity of supermassive black holes. Methods. We analyze the peculiar radio galaxy 3C 111, for which long-Term polarimetric observations are available. We make use of the high spatial resolution of…
The fate of terrestrial and riverine materials in a Mediterranean seagrass bed
2009
Neutral Iron Emission Lines From The Day-side Of KELT-9b -- The GAPS Programme With HARPS-N At TNG XX
2020
We present the first detection of atomic emission lines from the atmosphere of an exoplanet. We detect neutral iron lines from the day-side of KELT-9b (Teq $\sim$ 4, 000 K). We combined thousands of spectrally resolved lines observed during one night with the HARPS-N spectrograph (R $\sim$ 115, 000), mounted at the Telescopio Nazionale Galileo. We introduce a novel statistical approach to extract the planetary parameters from the binary mask cross-correlation analysis. We also adapt the concept of contribution function to the context of high spectral resolution observations, to identify the location in the planetary atmosphere where the detected emission originates. The average planetary li…
Tailoring Third-Harmonic Diffraction Efficiency by Hybrid Modes in High-Q Metasurfaces
2021
Metasurfaces are versatile tools for manipulating light; however, they have received little attention as devices for the efficient control of nonlinearly diffracted light. Here, we demonstrate nonlinear wavefront control through third-harmonic generation (THG) beaming into diffraction orders with efficiency tuned by excitation of hybrid Mie-quasi-bound states in the continuum (BIC) modes in a silicon metasurface. Simultaneous excitation of the high-Q collective Mie-type modes and quasi-BIC modes leads to their hybridization and results in a local electric field redistribution. We probe the hybrid mode by measuring far-field patterns of THG and observe the strong switching between (0,-1) and…
Third-harmonic generation in optical microfibers: From silica experiments to highly nonlinear glass prospects
2012
International audience; Using optical microfibers, phase matching between different propagation modes allows for third-harmonic generation (THG). After detailing the relevant phase matching conditions and overlap integrals, we provide a comparison between THG effective efficiencies in silica and tellurite glasses. We also explain the relatively easy, wideband, conversion that we observe experimentally in silica glass microfibers, from 155 mu m to the green, by the geometry of the tapering region.