IPG Photonics

About: IPG Photonics is a based out in . It is known for research contribution in the topics: Laser & Fiber laser. The organization has 903 authors who have published 1241 publications receiving 63339 citations.

X-ray Magnetic Circular Dichroism at Low Temperature

Abstract: This chapter is divided into three main parts In the first section we outline the reasons why low temperature measurements are necessary in x-ray absorption spectroscopy and more specifically in x-ray magnetic circular dichroism Emphasis is given to the different ways temperature can yield modifications on the experimental spectra In the second section, a description of the principles of normal 4He cryostat, pumped 4He cryostat and 3He-4He dilution refrigerator is given The third part presents recent dichroism experiments obtained at low temperature

Texture characterization of ERS-1 images by Regional Multifractal analysis

Abstract: Texture characterization aiming at landscape description was performed by multifractal analysis on radar images of the South Cameroon rain forest. The global characterization has been done with the Legendre spectrum. The local characterization has been done via the singularity maps of pointwise Holder exponents; then, multifractal spectra were obtained via a normalized estimator based upon the statistics of the singularity maps. The nature of local texture was therefore characterized by singularity spectra. Preliminary interpretations in terms of bio-geo-hydrological processes are given.

Low-threshold supercontinuum generation in polycrystalline media

Abstract: Until recently, the generation of super-octave continua in bulk materials at full repetition rates of femtosecond (fs) oscillators has been limited to a few special cases of Kerr lens mode-locked Ti:sapphire lasers. In 2019, we described a 3.4-octave fs source with 50 nJ pulse energy at the repetition rate of 78 MHz based on polycrystalline Cr:ZnS [Vasilyev et al., Optica6, 126 (2019)OPTIC82334-253610.1364/OPTICA.6.000126]. Here we explain the mechanism of fs supercontinuum generation in transition-metal doped polycrystalline II-VI semiconductors at relatively low (nJ-level) pulse energy. We demonstrate that this new supercontinuum regime is enabled by a complex, yet well-reproducible, interplay between the effects arising from the third-order nonlinearity, the quadratic nonlinearities, and thermal optical effects in the medium. We also demonstrate the control of fs pulse propagation in disordered $\chi ^{ (2)}$ media via the control of the material microstructure.

Where does a volcano break? Using self-potential reiteration to forecast the precise location of major destructive events on active volcanoes: the case study of the Piton de la Fournaise 2007 caldera collapse

Abstract: In April 2007, the Dolomieu caldera collapse was one of the most outstanding events of the last few decades at Piton de la Fournaise volcano. Forecasting the occurrence of such a destructive event is difficult but since then, the development of tools and monitoring networks has improved our knowledge of the dynamics of volcano instability. However, the precise location of volcano failure is still hard to constrain. In this paper, we show that reiteration of self-potential (SP) measurements taken at a one meter step-size along a 440-m-long profile prior to caldera collapse brings valuable insights on the most instable areas around the Dolomieu crater. SP signal dynamic reveals information not visible on one single SP acquisition. In particular, the SP dynamic highlights the presence of low cohesion/low strength materials at depth despite a lack of surface expression. Our survey at Piton de la Four-naise showed that preferential failure area can be precisely identified, at the meter scale. These results highlight the relevance of SP reiteration measurements as a tool for locating instabilities in both volcanic and non-volcanic environments.