Search results for "optics [X-ray]"
showing 10 items of 981 documents
On the Possibility of Miniature Diamond-Based Magnetometers Using Waveguide Geometries
2018
Micromachines 9(6), 276 (2018). doi:10.3390/mi9060276
Dielectric-loaded surface plasmon polariton waveguides: Figures of merit and mode characterization by image and Fourier plane leakage microscopy
2008
International audience; Waveguiding of surface plasmon polaritons by dielectric-loaded metal structures is studied in detail by combining numerical simulations and leakage radiation microscopy. These types of waveguides are first numerically investigated using the effective index model and the differential method. We analyzed systematically the influence of the ridge width and thickness of the waveguide on the properties of the surface plasmon guided modes. In particular we investigated the confinement factor of the modes and their associated propagation lengths. These two parameters can be optimized by adjusting the thickness of the dielectric layer. Waveguides loaded with thick and thin d…
The Single Molecule Probe: Nanoscale Vectorial Mapping of Photonic Mode Density in a Metal Nanocavity
2009
International audience; We use superresolution single-molecule polarization and lifetime imaging to probe the local density of states (LDOS) in a metal nanocavity. Determination of the orientation of the molecular transition dipole allows us to retrieve the different LDOS behavior for parallel and perpendicular orientations with respect to the metal interfaces. For the perpendicular orientation, a strong lifetime reduction is observed for distances up to 150 nm from the cavity edge due to coupling to surface plasmon polariton modes in the metal. Contrarily, for the parallel orientation we observe lifetime variations resulting from coupling to characteristic λ/2 cavity modes. Our results are…
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…
Dispersion managed self-similar parabolic pulses
2008
International audience; We describe the propagation of a parabolic self-similar pulse in an anomalous dispersive nonlinear fibre. Given the capacity of a linearly chirped parabolic pulse to retain its typical shape over a short propagation distance, we introduce the concept of dispersion managed self-similar pulses and outline potential benefits in terms of spectral broadening enhancement.
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…
Chalcogenide Microstructured Fibers for Infrared Systems, Elaboration, Modelization, and Characterization
2009
special issue " Fiber Optic Research in France " (Part III of III); International audience; Chalcogenide fibers present numerous possible applications in the IR field. For many applications, single mode fibers must be obtained. An original way is the realization of microstructured optical fibers (MOFs) with solid core. These fibers present a broad range of optical properties thanks to the high number of freedom degrees of their geometrical structure. In this context, we have developed MOFs for near and mid IR transmission with different geometries and properties such as multimode or endless single-mode operation, small or large mode area fibers. We have also investigated numerically the mai…
Enhanced nonlinear spectral compression in fibre by external sinusoidal phase modulation
2016
International audience; We propose a new, simple approach to enhance the spectral compression process arising from nonlinear pulse propagation in an optical fibre. We numerically show that an additional sinusoidal temporal phase modulation of the pulse enables efficient reduction of the intensity level of the side lobes in the spectrum that are produced by the mismatch between the initial linear negative chirp of the pulse and the self-phase modulation-induced nonlinear positive chirp. Remarkable increase of both the extent of spectrum narrowing and the quality of the compressed spectrum is afforded by the proposed approach across a wide range of experimentally accessible parameters.
Impact of amplitude jitter and signal-to-noise ratio on the nonlinear spectral compression in optical fibres
2017
International audience; We numerically study the effects of amplitude fluctuations and signal-to-noise ratio degradation of the seed pulses on the spectral compression process arising from nonlinear propagation in an optical fibre. The unveiled quite good stability of the process against these pulse degradation factors is assessed in the context of optical regeneration of intensity-modulated signals, by combining nonlinear spectral compression with centered bandpass optical filtering. The results show that the proposed nonlinear processing scheme indeed achieves mitigation of the signal's amplitude noise. However, in the presence of a jitter of the temporal duration of the pulses, the perfo…
Artificial neural networks for nonlinear pulse shaping in optical fibers
2020
International audience; We use a supervised machine-learning model based on a neural network to predict the temporal and spectral intensity profiles of the pulses that form upon nonlinear propagation in optical fibers with both normal and anomalous second-order dispersion. We also show that the model is able to retrieve the parameters of the nonlinear propagation from the pulses observed at the output of the fiber. Various initial pulse shapes as well as initially chirped pulses are investigated.