Improving the brightness of a multi-kilowatt single thin-disk laser by an aspherical phase front correction

We report on results obtained with an aspherical mirror to compensate for the phase front aberrations of a cw thin-disk laser with a single disk in the resonator. A record output power of 5?kW with a beam quality suitable for laser cutting (beam propagation factor M2=9.2) has been achieved.     

Synthesis and phase‐separation behavior of α,ω‐difunctionalized diblock copolymers

A series of diblock copolymers of n‐pentyl methacrylate and methyl methacrylate (PPMA/PMMA BCP) with one or two terminal functional groups was prepared by sequential anionic polymerization of PMA and MMA using an allyl‐functionalized initiator and/or and end‐capping with allyl bromide. Allyl functional groups were successfully converted into OH groups by hydroboration. The morphology in bulk was examined by temperature‐dependent small‐angle X‐ray measurements (T‐SAXS) and transmission electron microscopy (TEM) showing that functional groups induced a weak change in d‐spacings L₀ as well as in the thermal expansion behavior. T‐SAXS proved that the lamellar morphologies were stable over multiple heating/cooling cycles without order‐disorder transition (ODT) until 300 °C. While non‐functionalized BCP formed parallel lamellae morphologies, additional OH‐termination at the PMMA block forced in very thin films (ratio between film thickness and lamellar d‐spacing below 1) the generation of perpendicular lamellae morphology through the whole film thickness, as shown by Grazing‐incidence small‐angle X‐ray scattering experiments (GISAXS) measurements. Functionalized BCP were successfully used in thin films as templates for silica nanoparticles in an in‐situ sol–gel process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

A contribution to the identification of the E5 defect level as tri-vacancy (V3)

Silicon particle detectors in tracking devices for the high luminosity Large Hadron Collider will suffer from an extremely intense radiation field of mainly hadronic particles. The main radiation induced deep defect centres in silicon, responsible for the increase of the dark current and corresponding noise, are the cluster related defect levels E5 and E205a. This work confirms the identification of the E5 level as tri-vacancy (V₃). This defect transforms into the tri-vacancy-oxygen complex (V₃O) at temperatures above 200 °C. The defect concentrations were obtained by means of Deep Level Transient Spectroscopy (DLTS) and Thermally Stimulated Current technique (TSC) performed on float zone (FZ), epitaxially grown (Epi) and Magnetic Czochralski (MCz) silicon diodes, irradiated with 1 MeV neutrons and 23 GeV protons.     

Dielectric breakdown of Mott insulators in dynamical mean-field theory

Using nonequilibrium dynamical mean-field theory, we compute the time evolution of the current in a Mott insulator after a strong electric field is turned on. We observe the formation of a quasistationary state in which the current is almost time independent although the system is constantly excited. At moderately strong fields this state is stable for quite long times. The stationary current exhibits a threshold behavior as a function of the field, in which the threshold increases with the Coulomb interaction and vanishes as the metal-insulator transition is approached.     

Optical control of the refractive index of a single atom

We experimentally demonstrate the elementary case of electromagnetically induced transparency with a single atom inside an optical cavity probed by a weak field. We observe the modification of the dispersive and absorptive properties of the atom by changing the frequency of a control light field. Moreover, a strong cooling effect has been observed at two-photon resonance, increasing the storage time of our atoms twenty-fold to about 16 seconds. Our result points towards all-optical switching with single photons.     

Backscattering and sputtering with the monte-carlo program TRIM.SP

Abstract

The changes of the program TRIM.SP namely the vectorization and other minor changes since its first publication in 1984 are shortly described. Examples especially about backscattering and sputtering illustrate the possibilities which can be handled by the program.