Search results for "Absorption"
showing 10 items of 2701 documents
Error propagation from line parameters to spectra simulations. Illustration on high temperature methane.
2010
Astrophysical investigations generally need both complete and accurate spectroscopic databases. Despite continuous efforts in experimental and theoretical spectroscopic investigations, the lack of data in some spectral regions of interest is one of the main limitation of the presently available spectroscopic databases. Unfortunately information about missing data relevant to specific experimental conditions is rarely directly accessible from spectroscopic databases (focusing naturally on available data). Such information relies essentially on theoretical investigations which are equally limited to the present state of the art of modelling. The purpose of the talk is to show how multi-resolu…
Multi-Resolution error analysis of predicted absorption coefficients. Method and computer implementation. Application to the infrared spectrum of met…
2009
A general method for the estimation of the confidence interval of molecular absorption coefficients is presented. It combines statistical numerical experiments with analytical calculations. The method uses line parameter predictions (position and intensity) with known estimated uncertainties. The propagation of errors from line parameters to absorption coefficients or cross-sections are analyzed in detail as a function of the resolution. This work is especially intended to provide expert information for applications requiring theoretical predictions for which the present state of the art of line by line high-resolution modeling is not accurate enough to meet the experimental precision. As a…
Passively mode-locked laser based on an ultra-large dispersion Yb-doped fiber
2013
Summary form only given. We report on the first realization of a passively mode-locked oscillator featuring an ultra-large dispersion Yb-doped Bragg fiber. The gain medium is a double-clad Bragg fiber featuring a 20 μm Yb-doped core surrounded by a 120 μm inner cladding [1]. The 2 m long gain fiber is cladding-pumped with a fiber-coupled laser diode emitting at 976 nm. Passive mode locking is achieved by the combined actions of nonlinear polarization evolution and a SESAM. Mode-locking is initiated by optimizing the saturation criteria on the saturable absorber mirror using an adequate focusing lens. The emission wavelength of the oscillator is controlled using a passive spectral filter int…
Cascadability and efficiency of a saturable absorber device inserted into a SMF transmission line for future 160-Gbit/s all-optical reshaping applica…
2007
In this prospective work, we analyze the cascadability and reshaping properties of a quantum well microcavity saturable absorber (SA) device cascaded inside a RZ-signal SMF-based transmission line to annihilate the ghost-pulse phenomenon taking place in the "...01010101..." 160-Gbit/s 2-bit pattern.
Study of supercontinuum sources based on tellurite glass optical fibers for mid-infrared absorption spectroscopy applied to gas sensing
2015
This work focuses on the development of mid-infrared supercontinuum light sources and their application for gas detection through absorption spectroscopy. The study of supercontinuum sources is based on nonlinear ultrashort pulse propagation in tellurite glass (80TeO2-10ZnO-10Na2O) and used in three different forms, namely a thin bulk sample, a microstructured suspended-core fiber, and a tapered suspended-core fiber. These technical means adapt themselves to distinct laser sources commercially available, thus optimizing the implementation of ultrawide-band infrared light sources. Experimental observations are compared to corresponding numerical simulations, thus pointing out the different u…
X-ray irradiation influence on prototype Er3+-optical fibers: confocal luminescence study
2010
International audience; The integration of rare-earth doped optical fibers as part of fiber-based systems in space implies the development of waveguides tolerant to the radiation levels associated with the space missions. We report the spatial distribution, the photoluminescence (PL) properties of color centers and the related changes induced by X-rays radiation at different doses (50, 500 and 1000 krad) for two different prototypes of Er-doped optical fibers. Each sample (in the version pristine, X-irradiated and H2 loaded prior to radiation exposure) was characterized by confocal microscopy luminescence (CML) measurements in Visible range with Visible (488 nm) or UV (325 nm) laser light e…
Hyperfine structure of some near-infrared Xe I and Xe II lines
2011
International audience; This work reports on the experimental determination of the hyperfine splitting of the Xe I lines at 828.01 nm and 834.68 nm and the Xe II line at 834.72 nm. Measurements were performed by means of Doppler-free saturation spectroscopy in a low-pressure radio-frequency discharge. The absolute wavelength of all hyperfine components is obtained by way of a high-precision wavemeter backed-up with the absorption spectrum of the NO 2 molecule. We provide an accurate estimate of hyperfine constants for the lower level of the Xe II transition at 834.72 nm. The two Xe I transition outcomes of our experimental study are compared with data available in the literature.
All optical solition-based 2R regeneration at 170 Gbps
2010
[NMB4]; International audience; We report the numerical and experimental studies of a spectrally filtered-based all-optical 2R regenerator at 170 Gbps. The fiber device is combined with a fast saturable absorber. BER assessment exhibits a receiver sensitivity improvement.
Ultraviolet optical properties of silica controlled by hydrogen trapping at Ge-related defects
2007
We studied the effects induced by the ultraviolet-laser and -lamp exposure sequences on the twofold coordinated germanium (=Ge{sup {center_dot}}{sup {center_dot}}) and the H(II) center (=Ge{sup {center_dot}}-H) in silica. The H(II) centers, generated after the first laser irradiation stage by the trapping of atomic hydrogen H{sup 0} at the (=Ge{sup {center_dot}}{sup {center_dot}}), are destroyed by the subsequent lamp exposure with efficiency depending on photon energy. The H(II) photodestruction is activated from {approx}4 eV, and its cross section is here quantitatively measured, so giving the absorption profile of this center. Consistent with the observed correlated recovering of (=Ge{su…
Radiation-induced defects in fluorine-doped silica-based optical fibers: Influence of a pre-loading with H2
2009
International audience; We investigated the effects of 10-keV X-ray radiation on the transmission properties of F-doped optical fibers in the 200–850 nm range of wavelengths (1.5–6 eV). We also studied the influence of pre-loading this kind of fibers with hydrogen on its radiation sensitivity. Our results showed that, for our experimental conditions (pre-treatment with H2 several months before irradiation with diffusion of all the H2 out the fiber core and cladding before X-ray exposure), this pre-treatment increases the radiation-induced attenuation in the ultraviolet part (200–300 nm) of the spectrum. A previous H2-loading has no influence at greater wavelengths. The nature of the radiati…