A Passive Q-Switched Microchip Er/Yb Glass Laser Pumped by Laser Diode

A laser-diode-pumped 1.54-μm passive Q-switched erbium doped glass laser was reported. We utilize a laser diode with wavelength of 973nm to pump a 1-mm Er/Yb co-doped phosphate glass with the erbium and ytterbium concentrations of 1 wt.% and 21 wt.%, respectively. A Co^2＋ ：MgAl2O4 slab crystal was used as a passive Q- switcher. Q-switched pulses with repetition frequency of 800Hz, width of 7.4ns, peak power of 2.2kW and average power of 13.3 m W were obtained when absorbed pump power was 4 75 m W. A sandwich structure of the Q- switched microchip Er/Yb glass laser was demonstrated, which shows shorter pulse width of 6.8 ns. Dependences of pulse duration and repetition frequency on pump power were also investigated.     

Kinetics of the nematic ordered phase growth during a temperature quench of an isotropic siloxane-azomethine polymer

Kinetics of the nucleus growth during a deep temperature quench across the isotropic to nematic phase transition was experimentally investigated for a siloxane-azomethine polyether at cooling rates of 10 and 20°C min^-1. Nematic droplets revealed in the optical images during the phase separation were treated statistically and the resulting statistical size distributions were described using the model of reversible aggregation. Analysis of the time-dependent distribution parameters allowed two processes involved in liquid crystal phase ordering to be identified: nucleus growth and nucleus coarsening. Both regimes are quantitatively described using the universal growth law.     

1,5-Di­amino-1H-1,2,3,4-tetrazole

In the title compound, CH₄N₆, the tetrazole ring is planar to within 0.001 (1) Å. The 5-amino group is conjugated with the π-system of the tetrazole ring. In contrast, the N atom of the 1-­amino group is sp³ hybridized and is not conjugated with the π system of the tetrazole ring. All H atoms are localized at the exocyclic N atoms. The mol­ecules are connected by N—H⃛N hydrogen bonds, forming an infinite three-dimensional framework.     

Resonance scattering on In impurity in Pb0.4Sn0.6Te solid solutions

The Hall coefficient and resistivity were measured on a series of samples of InTe in Pb_0.4Sn_0.6Te solid solutions with varying indium content from 0 to 5 molar%. All samples show a p-type conductivity with the concentration of holes 10¹⁹ cm⁻³ at 77 K. A considerable decrease of mobility calculated from the measurements was observed in the samples with high content of In. The contribution to the mobility, directly related to the scattering of holes into In atoms, was determined, and the scattering crosssection was estimated. We observed a drastic increase in the scattering crosssection with the rise of In content, which can be explained by the resonance scattering of holes into the band of quasi-local states of In. This result can also be explained with the use of the Breit–Wigner formula. The location of the In states in the valence band was also calculated using the Kane model.     

Computing o-minimal topological invariants using differential topology

We work in an o-minimal expansion of a real closed field. Using piecewise smoothness of definable functions we define the topological degree for definable continuous functions. Using this notion of the degree we obtain a new proof for the existence of torsion points in a definably compact group, and also a new proof of an o-minimal analogue of the Brouwer fixed point theorem.

     

A global attractivity criterion for nonlinear non-autonomous difference equations

We establish a discrete version of the celebrated Yorke and Wright 3/2-stability criterion for a family of strongly nonlinear non-autonomous difference equations of the form xn+1=xn+anfn(xn,…,xn−k).     

Water vapour line assignments in the 9250-26 000 cm frequency range

Line parameters for water vapour in natural abundance have recently been determined for the 9250-13 000 cm⁻¹ region [M.-F. Mérienne, A. Jenouvrier, C. Hermans, A.C. Vandaele, M. Carleer, C. Clerbaux, P.-F. Coheur, R. Colin, S. Fally, M. Bach, J. Quant. Spectrosc. Radiat. Transfer 82 (2003) 99] and the 13 000-26 000 cm⁻¹ region [P.-F. Coheur, S. Fally, M. Carleer, C. Clerbaux, R. Colin, A. Jenouvrier, M.-F. Mérienne, C. Hermans, A.C. Vandaele, J. Quant. Spectrosc. Radiat. Transfer 74 (2002) 493] using a high-resolution Fourier-transform spectrometer with a long-path absorption cell. These spectra are analysed using several techniques including variational line lists and assignments made. In total, over 15 000 lines were assigned to transitions involving more than 150 exited vibrational states of H₂¹⁶O. Twelve new vibrational band origins are determined and estimates for a further 16 are presented.     

One-pot synthesis of monosubstituted aryl(hetaryl)acetylenes by direct introduction of the CCH residue into arenes and hetarenes

A convenient one-pot synthesis of aryl(hetaryl)acetylenes by cross-coupling of aryl(hetaryl)iodides with acetylene in presence of PdCl₂(Ph₃)₂, CuI and K₂CO₃ in DMF has been developed.     

Fiber Bragg Grating Writing by Interferometric or Phase-Mask Methods Using High-Power Excimer Lasers

This paper reports the development of high-power excimer lasers with enhanced spatial and temporal coherence. These excimer lasers are applicable to writing fiber Bragg gratings by interferometric or phase-mask techniques. An excimer laser with a novel unstable resonator is analyzed with respect to its suitability to the production of passive fiber-optic components and in terms of production flexibility, efficiency, and reliability. A survey of applicability of this tool to short-and long-period fiber Bragg gratings is presented.