Journal ArticleDOI
Mode evolution in optical resonators with a radial gain profile.
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TLDR
A Fox and Li analysis for a laser resonator with a radially varying gain yields a picture of the mode evolution dynamics and a steady-state mode distribution which are different from the constant-gain case.Abstract:
A Fox and Li analysis [Bell Syst. Tech J. 40, 453 (1961); Proc. IEEE 51, 80 (1963); IEEE J. Quantum Electron QE-4, 460 (1968)] for a laser resonator with a radially varying gain yields a picture of the mode evolution dynamics and a steady-state mode distribution which are different from the constant-gain case. When an axially maximal gain is sharply peaked, the mode-settling time is markedly reduced and the final mode distribution is more tightly focused. When the gain distribution is sharply annular, an annular or ``doughnut''-shaped mode develops. In some intermediate cases, which may be relevant to some gas lasers, a stable transverse mode never definitively evolves. Misalignments of the gain with the cavity yield distortions to the mode shape and these are also explored.read more
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Electronic correlation effects in transition-metal sulfides
TL;DR: In this paper, the DFT + U method was used to predict the structural and electronic properties of transition-metal sulfides formed by 3D transition metal atoms, including magneto-volume effects and magneto structural effects.
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Ab initio density functional studies of transition-metal sulphides: I. Crystal structure and cohesive properties
Abstract: The structural and cohesive properties of more than thirty transition-metal sulphides of various stoichiometries and crystal structures have been investigated using density functional theory, with the aim of establishing a correlation between the strength of the metal - sulphur bond and the catalytic activities of these materials. It is shown that the local density approximation has a tendency to overestimate the strength of the bonding. The overbinding manifests itself in the prediction of too small atomic volumes and too large cohesive energies. Non-local corrections to the local exchange - correlation functional in the form of a generalized-gradient approximation correct the overbinding (albeit with a certain tendency to overcorrect, especially for the sulphides of the heavy transition metals) and result in accurate structural prediction and cohesive energies. A correlation between the sulphur - metal bond strength and the catalytic activities is established.
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Magnetism and magneto-structural effects in transition-metal sulphides
David Hobbs,Jürgen Hafner +1 more
TL;DR: In this article, the effect of magnetic ordering on a wide range of transition-metal sulphides has been investigated and it was shown that the magnetic ordering leads to a substantial increase of the equilibrium volume and a reduction in the axial ratio of the NiAs-type lattice.
Journal ArticleDOI
Energetics of Oxidation in MoS2 Nanoparticles by Density Functional Theory
TL;DR: In this paper, density functional theory is used to determine the energetics of atomic oxygen substitution in an infinite single MoS2 trilayer and on the edges of six structurally distinct MOS2 nanoparticles.
Journal ArticleDOI
Optimum laser beam profile for maximum energy extraction from a saturable amplifier
TL;DR: In this article, the optimum laser beam profile for a low-gain saturable amplifier is determined analytically, and it is shown that the optimum is broad in the space of functions so that a large class of beam shapes can be nearly optimum.