389 research outputs found
Medium-Energy Proton-Nucleus Elastic Scattering in the Impulse Approximation
This work was supported by National Science Foundation Grants PHY 76-84033A01, PHY 78-22774, and Indiana Universit
RGB generation by four-wave mixing in small-core holey fibers
We report the generation of white light comprising red, green, and blue spectral bands from a frequency-doubled fiber laser by an efficient four-wave mixing process in submicron-sized cores of microstructured holey fibers. A master-oscillator power amplifier (MOPA) source based on Yb-doped fiber is employed to generate 80 ps pulses at 1060 nm wavelength with 32 MHz repetition rate, which are then frequency-doubled in an LBO crystal to generate up to 2 W average power of green light. The green pump is then carefully launched into secondary cores of the cladding of photonic bandgap fibers. These secondary cores with diameters of about 400 to 800 nm act as highly nonlinear waveguides. At the output, we observe strong red and blue sidebands which, together with the remaining green pump light, form a visible white light source of about 360 mW. The generating process is identified as four-wave mixing where phase matching is achieved by birefringence in the secondary cores which arises from non-symmetric deformation during the fiber fabrication. Numerical models of the fiber structure and of the nonlinear processes confirm our interpretation. Finally, we discuss power scaling and limitations of the white light source due to the damage threshold of silica fibers
A single-mode, high index-contrast, lead silicate glass fibre with high nonlinearity, broadband near-zero dispersion at telecommunication wavelengths
We report on the design, fabrication and characterization of a single-mode W-type lead silicate glass fibre with flattened and near-zero dispersion profile at telecom wavelengths and high nonlinearity of 820 W-1km-1 at 1.55 µm
Phase sensitive amplification in a highly nonlinear lead-silicate fibre
We experimentally demonstrate phase-sensitive amplification in a highly nonlinear lead-silicate W-type fibre. A phase-sensitive gain swing of 6dB was observed in a 1.56m sample of the fibre for a total launched power of 33dBm
Flat, broadband supercontinuum generation at low pulse energies in a dispersion-tailored lead-silicate fibre
We report flat, broadband supercontinuum generation at low pump pulse energies (69pJ 740fs pulses at 1540nm) in a lead-silicate fibre providing a unique combination of high nonlinearity (820W-1km-1) and a flat near-zero dispersion profile
Influence of porosity on the deformation behaviour of systems with nanostructured thermal barier coatings
Based on the principal concepts of physical mesomechanics that take into account reversible structural-phase transformations in the rotational-wave flows at the interfaces, a new modification of the multilevel discrete-continuous method of excitable cellular automata (ECA) has been developed. The new modification explicitly takes into account the porosity and the nanocrystalline structure. Also, algorithms for calculating the local moments of forces and the angular velocities of microrotations arising in a structurally heterogeneous medium have been implemented. The model has been complemented by the dissipation conditions expressed for mechanical energy flows. On the basis of the method of excitable cellular automata, some numerical experiments on thermal loading of three-layered compositions with the intermediate layers of different structures have been carried out. It is shown that nanostructuring of the intermediate sublayer and the introduction of nanoporosity gives rise to a positive effect on the relaxation ability of thermal barrier coatings
Applications of highly nonlinear dispersion tailored lead silicate fibres for high speed optical communications
Recent advances in optical fibre technology, most notably in the area of microstructured optical fibres (MOFs), offer a host of new opportunities within future high speed communication systems. Herein we review how our recent progress on the implementation of lead silicate fibre designs, allowing both flexible dispersion control and a high effective nonlinearity, can be integrated into various all-optical signal processing devices for high speed optical communication systems. Highly nonlinear lead silicate fibres have already proven to be well suited for achieving efficient four-wave mixing (FWM) due to their high effective nonlinear coefficient, low dispersion profile and short length
Phenomenological and Microscopic Optical-Model Descriptions of 99 MeV 6-Li Scattering
This work was supported by National Science Foundation Grants PHY 76-84033A01, PHY 78-22774, and Indiana Universit
Halo Excitation of He in Inelastic and Charge-Exchange Reactions
Four-body distorted wave theory appropriate for nucleon-nucleus reactions
leading to 3-body continuum excitations of two-neutron Borromean halo nuclei is
developed. The peculiarities of the halo bound state and 3-body continuum are
fully taken into account by using the method of hyperspherical harmonics. The
procedure is applied for A=6 test-bench nuclei; thus we report detailed studies
of inclusive cross sections for inelastic He(p,p')He and
charge-exchange Li(n,p)He reactions at nucleon energy 50 MeV. The
theoretical low-energy spectra exhibit two resonance-like structures. The first
(narrow) is the excitation of the well-known three-body resonance. The
second (broad) bump is a composition of overlapping soft modes of
multipolarities whose relative weights depend on
transferred momentum and reaction type. Inelastic scattering is the most
selective tool for studying the soft dipole excitation mode.Comment: Submitted to Phys. Rev. C., 11 figures using eps
Studies of Excited States in 208-Pb by Inelastic Proton Scattering at 100 MeV
This work was supported by the National Science Foundation Grant NSF PHY 78-22774 A02 & A03 and by Indiana Universit
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