25,483 research outputs found
Transverse effects in multifrequency Raman generation
The theory of ultrabroadband multifrequency Raman generation is extended, for the first time, to allow for beam-propagation effects in one and two transverse dimensions. We show that a complex transverse structure develops even when diffraction is neglected. In the general case, we examine how the ultrabroadband multifrequency Raman generation process is affected by the intensity, phase quality, and width of the input beams, and by the length of the Raman medium. The evolution of power spectra, intensity profiles, and global characteristics of the multifrequency beams are investigated and explained. In the two-dimensional transverse case, bandwidths comparable to the optical carrier frequency, spanning the whole visible spectrum and beyond, are still achievable
Spontaneous spatial fractal pattern formation in absorptive systems
We predict, for the first time to our knowledge, that purely-absorptive nonlinearity can support spontaneous spatial fractal pattern formation. A passive optical ring cavity with a thin slice of saturable absorber is analyzed. Linear stability analysis yields threshold curves for Turing (static) instabilities with features proposed as characteristics of potential fractal pattern formation. Numerical simulations of the fully-nonlinear dynamics, with both one and two transverse dimensions, confirm theoretical predictions
Kaleidoscope laser
We report the first calculations of mode patterns of unstable-cavity lasers with truly two-dimensional transverse geometries. A detailed account of numerical techniques, incorporating a nonorthogonal beam-propagation method, and results for cavities with a range of transverse symmetries, such as regular polygonal and rhomboid, are presented. In view of the beautiful complexity of the eigenmodes predicted, a novel kaleidoscope laser is proposed
Optical Production of Stable Ultracold Sr Molecules
We have produced large samples of ultracold Sr molecules in the
electronic ground state in an optical lattice. The molecules are bound by 0.05
cm and are stable for several milliseconds. The fast, all-optical method
of molecule creation via intercombination line photoassociation relies on a
near-unity Franck-Condon factor. The detection uses a weakly bound vibrational
level corresponding to a very large dimer. This is the first of two steps
needed to create Sr in the absolute ground quantum state. Lattice-trapped
Sr is of interest to frequency metrology and ultracold chemistry.Comment: 5 pages, 3 figure
DEKAS - An evolutionary case-based reasoning system to support protection scheme design
This paper describes a decision support system being developed in conjunction with two UK utility companies to aid the design of electrical power transmission protection systems. A brief overview of the application domain is provided, followed by a description of the work carried out to date concerning the development and deployment of the Design Engineering Knowledge Application System (DEKAS). The paper then discusses the provision of intelligent decision support to the design engineer through the application of case-based reasoning (CBR). The key benefits from this will be outlined in conjunction with a relevant case study
The Influence of Formulation, Buffering, pH and Divalent Cations on the Activity of Endothall on Hydrilla.
Endothall has been used as an aquatic herbicide for more
than 40 years and provides very effective weed control of
many weeds. Early research regarding the mechanism-of-action
of endothall contradicts the symptomology normally associated
with the product. Recent studies suggest endothall
is a respiratory toxin but the mechanism-of-action remains
unknown. To further elucidate the activity of endothall, several
endothall formulations were evaluated for their effects
on ion leakage, oxygen consumption and photosynthetic oxygen
evolution from hydrilla shoot tips. The influence of pH,
buffering and divalent cations was also evaluated. (PDF contains 6 pages.
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