Inhomogeneous Gain Saturation in EDF: Experiment and Modeling

Erbium-Doped Fiber Amplifiers can present holes in spectral gain in Wavelength Division Multiplexing operation. The origin of this inhomogeneous saturation behavior is still a subject of controversy. In this paper we present both an experimental methods and a gain's model. Our experimental method allow us to measure the first homogeneous linewidth of the 1.5 $\mu$m erbium emission with gain spectral hole burning consistently with the other measurement in the literature and the model explains the differences observed in literature between GSHB and other measurement methods

Photon-avalanche upconversion of red light into blue light in a thulium-doped fluorozirconate fibre

We report the investigation of the photon-avalanche effect in heavily thulium-doped fluorozirconate fibre. Pumping at red wavelengths, which are not resonant with the ground-state absorption, gives blue emission at 450nm and 480nm

Spectroscopic signature of phosphate crystallization in Erbium-doped optical fibre preforms

In rare-earth-doped silica optical fibres, the homogeneous distribution of amplifying ions and part of their spectroscopic properties are usually improved by adding selected elements, such as phosphorus or aluminum, as structural modifier. In erbium ion (Er3+) doped fibres, phosphorus preferentially coordinates to Er3+ ions to form regular cages around it. However, the crystalline structures described in literature never gave particular spectroscopic signature. In this article, we report emission and excitation spectra of Er3+ in a transparent phosphorus-doped silica fibre preform. The observed line features observed at room and low temperature are attributed to ErPO4 crystallites

Search for anisotropic effects of hcp solid helium on optical lines of cesium impurities

The anisotropic effect of a hcp 4He solid matrix on cesium atoms has been proposed as a tool to reveal the parity violating anapole moment of its nucleus. It should also result in splitting the D2 optical excitation line in a way depending on the light polarization. An experimental investigation has been set up using oriented hcp helium crystals in which cesium metal grains are embedded. Atoms are created by laser sputtering from this grains. Optical absorption spectra of the D2 line have been recorded in the temperature range of 1.0 to 1.4 K at liquid/solid coexistence pressure by monitoring the fluorescence on the D2 line at 950 nm. No significant effect of the light polarization has been found, suggesting a statistically isotropic disordered solid environment for the cesium atoms.Comment: The original publication will be available at http://www.springerlink.co

Blue avalanche upconversion in Tm:ZBLAN fibre

We report the investigation of the photon avalanche effect in heavily doped Tm:ZBLAN fibre at room temperature. Pumping at 630nm to 650nm, which is not resonant with the ground state absorption, gives intense blue emissions at 450nm and 480nm. The time evolution of the absorption and emission show a slow decaying oscillation before steady state is reached

Using Markov chain Monte Carlo methods for estimating parameters with gravitational radiation data

We present a Bayesian approach to the problem of determining parameters for coalescing binary systems observed with laser interferometric detectors. By applying a Markov Chain Monte Carlo (MCMC) algorithm, specifically the Gibbs sampler, we demonstrate the potential that MCMC techniques may hold for the computation of posterior distributions of parameters of the binary system that created the gravity radiation signal. We describe the use of the Gibbs sampler method, and present examples whereby signals are detected and analyzed from within noisy data.Comment: 21 pages, 10 figure

Universal Code Equivalent of a Yeast Mitochondrial lntron Reading Frame Is Expressed into E. coli as a Specific Double Strand Endonuclease

International audienceThe intron of the mitochondrial21S rRNA gene of Sac-charomyces cerevisiae (rl intron) possesses a 235 codon long internal open reading frame (rl ORF) whose translation product determines the duplicative transposition of that intron during crosses between intron-plus strains (omega+) and intron-minus ones (omega-). Using site-directed mutagenesis, we have constructed a universal code equivalent of the rl ORF that, under appropriate promoter control, allows the overexpression in E. coli of a protein identical to the mitochondrial intron encoded "transposase". This protein exhibits a double strand endonuclease activity specific for the omega-site. This finding demonstrates , for the first time, the enzymatic activity of an intron encoded protein whose function is to promote the spreading of that intron by generating double strand breaks at a specific sequence within a gene

Status, scientific results and technical improvements of the NBH on TCV tokamak

The TCV tokamak contributes to physics understanding in fusion reactor research by a wide set of experimental tools, like flexible shaping and high power ECRH. A 1MW, 25 keV deuterium heating neutral beam (NB) has been installed in 2015 and it was operated from 2016 in SPC-TCV domestic and EUROfusion MST1 experimental campaigns ((similar to)50/50%). The rate of failures of the beam is less than 5%. Ion temperatures up to 3.5 keV have been achieved in ELMy H-mode, with a good agreement with ASTRA predictive simulations. The NB enables TCV to access ITER-like beta(N) values (1.8) and T-e/T-i (similar to)1, allowing investigations of innovative plasma features in ITER relevant ELMy H-mode. The advanced Tokamak route was also pursued, with stationary, fully non-inductive discharges sustained by ECCD and NBCD reaching beta(similar to)(N)1.4-1.7. Real-time control of the NB power has been implemented in 2018 and presented together with the statistics of NB operation on the TCV. During commissioning, the NB showed unacceptable heating of the TCV beam duct, indicating a higher power deposition than expected on duct walls. A high beam divergence has been found by dedicated measurement of 3-D beam power density distribution with an expressly designed device (IR measurement on tungsten target)