Effects of spatial hole burning in 888?nm pumped, passively mode-locked high-power Nd:YVO4 lasers

We report on an experimental study of 888?nm pumped, passively mode-locked, high-power Nd:YVO₄ lasers with an enhanced cavity design, involving spatial hole burning (SHB) in the active medium. We observed a significant pulse shortening due to the concept of ??Gain-at-the end,?? despite using long gain length up to 30?mm. A?31.6?W average output power TEM₀₀ Nd:YVO₄ oscillator, providing 16.2?ps pulses at an repetition rate of 96?MHz is presented. The pulse duration turns out to be primarily a function of the effective gain length, which can be explained by means of SHB. A?further pulse shortening with decreasing gain length down to 9.5?ps at 11.1?W average output power is demonstrated.     

Localization of solitons: linear response of the mean-field ground state to weak external potentials

Two aspects of bright matter?Cwave solitons in weak external potentials are discussed. First, we briefly review recent results on the Anderson localization of an entire soliton in disordered potentials, as a paradigmatic showcase of genuine quantum dynamics beyond simple perturbation theory. Second, we calculate the linear response of the mean-field soliton shape to a weak, but otherwise arbitrary, external potential, with a detailed application to lattice potentials.     

Thermal analysis and efficient high power continuous-wave and?mode-locked thin disk laser operation of Yb-doped sesquioxides

We report on thermal conductivity analysis and thin disk laser power scaling of Yb:Lu₂O₃, Yb:Sc₂O₃, and Yb:LuScO₃. Using a volume Bragg-grating stabilized pump diode we have obtained cw output powers up to 301?W with optical-to-optical efficiencies of up to 73%. In mode-locked operation of an Yb:Lu₂O₃ thin disk laser 141?W of average output power with 738 fs pulses and an optical-to-optical efficiency of 40% were achieved.     

Femtosecond relaxation kinetics of highly excited \mathrm{M}_{\mathrm{Na}}^{**} states in CaF2 at 3.2 eV and 4.7 eV

Femtosecond (fs) laser pulses at variable delay times allowed us to track the fast non-radiative transitions between the manifold of highly excited $\mathrm{M}_{\mathrm{Na}}^{**}$ states to the lower lying fluorescent $\mathrm{M}_{\mathrm{Na}}^{*}$ state in CaF₂. Two distinct $\mathrm{M}_{\mathrm{Na}}^{**}$ states of the manifold at 3.16?eV ( $\mathrm{M}_{\mathrm{Na}2}^{**}$ ) and 4.73?eV ( $\mathrm{M}_{\mathrm{Na}3}^{**}$ ) were populated using the second (SH) and third harmonics (TH) of fs laser light at 785?nm. The population kinetics of the fluorescent $\mathrm{M}_{\mathrm{Na}}^{*}$ state in the 2?eV excitation energy range was revealed by depleting its fluorescence centered at 740?nm using fundamental near infrared (NIR) fs laser pulses. The related time constants for $\mathrm{M}_{\mathrm{Na}2,3}^{**}{\sim}{>} \mathrm{M}_{\mathrm{Na}}^{*}$ relaxation amounted to 1.0±0.14?ps and 3.0±0.3?ps upon SH and TH excitation, respectively.     

Ultrafast laser writing of optical waveguides in ceramic Yb:YAG: a study of thermal and non-thermal regimes

We report the improvement of ultrafast laser written optical waveguides in Yb:YAG ceramics by tailoring the presence of heat accumulation effects. From a combination of ytterbium micro-luminescence and micro-Raman structural analysis, maps of lattice defects and stress fields have been obtained. We show how laser annealing can strongly reduce the concentration of defects and also reduce compressive stress, leading to an effective 50% reduction in the propagation losses and to more extended and symmetric propagation modes.     

Terrestrial gamma exposure in the granodiorite area of Bergama (Pergamon)�CKozak, Turkey

As higher radiation levels are associated with granite and Bergama (Pergamon) has increasingly become a large market for granite use over the last years, an extensive investigation was started in 2009. Samples from the granites and soils underlying this area were collected and analyzed by HPGe gamma spectrometry system. The specific activities of the naturally occurring radionuclides ²²⁶Ra, ²³²Th, and ⁴⁰K were found to be in the range of 29?C111 Bq kg^?1 for ²²⁶Ra, 35?C87 Bq kg^?1 for ²³²Th and 698?C1100 Bq kg^?1 for ⁴⁰K in granite samples. The ranges of ²²⁶Ra, ²³²Th, and ⁴⁰K activity concentrations for soils were 32?C82, 42?C88 and 667?C1127 Bq kg^?1, respectively. From these data radiological parameters were calculated and compared with respective data from the UNSCEAR reports.     

Efficient catalytic systems based on paramagnetic closo-ruthenacarboranes for the controlled synthesis of polymers

Novel catalytic systems were proposed for controlled radical polymerization of vinyl monomers. These systems are based on the paramagnetic (17-electron) closo-complex, namely, 3,3-(dppb)-3-Cl-closo-3,1,2-RuC₂B₉H₁₁ (1, dppb is 1,4-bis(diphenylphosphino)butane) and its mono(P-phenylene)- and di(P,P-ortho-phenylene)cycloboronated derivatives, namely, (R = H, n = 10 (2); R = Me, n = 8 (3)) and (4). With the polymerization of methyl methacrylate as an example, the effect of the steric hindrances in complexes 1?C4 on the synthesis and molecular-weight characteristics of the resulting polymers was analyzed. In the presence of aliphatic amines, the polymerization rate increases substantially and the catalyst concentration can be lowered without losing control of the process. The structure of 17-electron complex 3 in the solid state and its paramagnetic nature were confirmed by X-ray diffraction and ESR spectroscopy.     

The complex Eu(phen)L3��5CH2Cl2 (HL is 1,3-bis(1,3-dimethyl-1H-pyrazol-4-yl)propane-1,3-dione): synthesis, crystal structure, and luminescent properties

A reaction of Eu(NO₃)₃·6H₂O with the novel heterocyclic ligand 1,3-bis(1,3-dimethyl-1H-pyrazol-4-yl)propane-1,3-dione and 1,10-phenanthroline in the presence of NaOH gave the complex Eu(phen)L₃·5CH₂Cl₂. The crystal structure of the complex was determined by single-crystal X-ray diffraction. The coordination polyhedron {EuO₆N₂} is a tetragonal antiprism. The complex shows bright orange-red luminescence in both the solid state and solution.     

Collapse transition in thin films of poly(methoxydiethylenglycol acrylate)

The thermal behavior of poly(methoxydiethylenglycol acrylate) (PMDEGA) is studied in thin hydrogel films on solid supports and is compared with the behavior in aqueous solution. The PMDEGA hydrogel film thickness is varied from 2 to 422?nm. Initially, these films are homogenous, as measured with optical microscopy, atomic force microscopy, X-ray reflectivity, and grazing-incidence small-angle X-ray scattering (GISAXS). However, they tend to de-wet when stored under ambient conditions. Along the surface normal, no long-ranged correlations between substrate and film surface are detected with GISAXS, due to the high mobility of the polymer at room temperature. The swelling of the hydrogel films as a function of the water vapor pressure and the temperature are probed for saturated water vapor pressures between 2,380 and 3,170?Pa. While the swelling capability is found to increase with water vapor pressure, swelling in dependence on the temperature revealed a collapse phase transition of a lower critical solution temperature type. The transition temperature decreases from 40.6?°C to 36.6?°C with increasing film thickness, but is independent of the thickness for very thin films below a thickness of 40?nm. The observed transition temperature range compares well with the cloud points observed in dilute (0.1?wt.%) and semi-dilute (5?wt.%) solution which decrease from 45?°C to 39?°C with increasing concentration.     

Determination of N-acetylcysteine via its effect on the aggregation of gold nanoparticles

The effect of thiol compounds on the kinetics of the aggregation of gold nanoparticles in the presence of the cationic surfactant cetyltrimethyl ammonium bromide has been studied. It was applied to the determination of N-acetylcysteine using the stopped-flow mixing technique along with light scattering detection. The signal obtained was measured after about 5?s, and gave the analytical information for a calibration graph in the concentration range from 2.9 to 60???mol?L^?1 of N-acetylcysteine, and a detection limit of 0.87???mol?L^?1. The effect of other thiols on the system is also described. The relative standard deviation ranges between 0.6% and 3.5%. The method was applied to the determination of N-acetylcysteine in several pharmaceutical samples with recoveries that range from 97.7% to 101.1%.