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.

Large mode area fiber for low-loss transmission and amplification of single mode lasers

Abstract: A large mode area optical fiber includes a large diameter core (d1 up to 60μm), and a first cladding (diameter d2) wherein the difference between refractive index (n1 ) in the core and the first cladding (n2) is very small (Δn 0.4) (n3 is preferably less than 1.3). The small change in refractive index between the core and inner cladding combined with a large change in refractive index between the first cladding and second cladding provides a significantly improved single mode holding waveguide.

Incorporation of Cr3+ in dickite: a spectroscopic study

Abstract: We have investigated a well-ordered sample of natural Cr-bearing dickite from Nowa Ruda (Lower Silesia, Poland) using electron paramagnetic resonance (EPR) at X- and Q-band frequencies (9.42 and 33.97 GHz, respectively) and optical diffuse reflectance spectroscopy. The observation of the spin-forbidden transitions at 15500 and 14690 cm−1 allows us to unambiguously identify the major contribution of octahedrally coordinated Cr3+ ions in the optical spectrum. The X- and Q-band EPR spectra show two superposed Cr3+ signals. The corresponding fine-structure parameters were determined at room temperature and 145 K. These results suggest the substitution of Cr3+ for Al3+ in equal proportions in the two unequivalent octahedral sites of the dickite structure. In kaolin group minerals, the distortion around Cr3+ ions (λ≈ 0.2–0.4) in Al sites is significantly less rhombic than that observed around Fe3+ ions (λ≈ 0.6–0.8).

Jamming transition of a granular pile below the angle of repose

Abstract: We experimentally study the relaxation towards mechanical equilibrium following the surface avalanche of a granular pile and discuss it in the general context of glassy materials and jamming transition. Two coexisting dynamics are observed in the surface layer: a short time exponential decay related to rapid isolated grains displacements, and intermittent reactivation bursts consisting in spatially correlated moves. The competition of both dynamics results in long-lived intermittent transients, the total duration of which can last more than a thousand of seconds. The typical time-scales, and the two-time relaxation function of these transients are measured. Analyzing the response of the surface layer to localized perturbations provides new evidence for spatial correlations. We further analyse the relaxation function in a probabilistic framework, which allows to discuss different possible scalings according to the choice of specific hypothesis. Following some considerations on the observed time-scales, we finally discuss the similarities with aging systems which are suggested by our description of the observed dynamics.

Effective medium approximation and exact formulae for electrokinetic phenomena in porous media

Abstract: Electrokinetic phenomena in porous media are studied by application of the effective medium theory and the theory of duality transformation. We deduce new exact relations and analytical formulae for the effective constants of the macroscopic tensor. We also prove that the effective tensors obtained by these approaches coincide for 2D problems. The obtained results for the electrokinetic processes are closely related to similar results derived for piezoelectric composites because of a common mathematical background.