In mechanics of materials it is important to know the stress-strain relation of each material in order to understand their behaviour under different loads. The brick is one of the most used materials in structural mechanics and they are always under loads. This work is implemented using one beam and the speckles created by its reflection. Strain field measurement with noninvasive techniques is needed in order to sense rubber-like materials. We present an experimental approach that describes the mechanical behavior of structural materials under compression tests, which are done in a universal testing machine. In this work we show an evaluation of the displacement field obtained by digital image correlation allowing us to evaluate the heterogeneous strain field evolution observed during these test.
Metallo Dielectric Photonic Crystals formed by same periodicity metallic inserts in a Dielectric Photonic Crystal show
three kind of band gaps, those at the well know dielectric band gap, the ones attributed to the absorption of metal to low
frequencies and a new class of metallic bandgaps. Numerical studies have confirmed that while the dielectric band gap
width is basically described by the refraction index contrast, the width of the metallic band is described by the thickness
of the metal inserts. In this work we carry on the corresponding analytical analysis of both band gaps for this one
dimensional ternary dielectric-dielectric-metal structure. The stack that we are proposing is a quarter-wave for the
dielectrics and the thickness of the metallic layers is changed as a free parameter. Using standard transfer matrix
formalism, we find a closed form of the dispersion relation and from it; we have analytically demonstrated the formation
and width of the dielectric band gap and its metallic perturbation, as well as those of the additional metallic band gap.
Communication systems require devices that allow rapid distribution of signals to multiple users. We presented a
proposal for a demultiplexer based on the fanning effect. Beam fanning is a process similar to two-beam coupling, except
in this case, in where only one beam is incident on the material and its energy is transferred into scattered light. As a
result of the energy transfer, scattered light is amplified, and a "fan" is observed. Since energy transfer direction can be
changed by switching the polarity of the applied electric field, beam fanning effect can be maximized or minimized on
depending of the polarity. We propose an optical router method with the photorefractive beam-fanning. In this method, a
Gaussian modulated beam passing through a photorefractive BaTiO3 crystals spreads into a some beams that arises from
stimulated scattering. This fanning can be controlled changing the polarization of the beam or the incident angle toward
the crystal. Each scattered beam maintains the input modulated frequency in a wide range. Our results show the possible
application of the fanning effect as an optoelectronic demultiplexer.
We discuss a structured 3D Dielectric Photonic Crystal with both a metallic core and a metallic shell. We
discuss the role of each one, the stack, the core as well as the cavity formed between the core and the
shell. The low frequency metallic core features becomes much more significant as it gets smaller and get
diluted by the cavity.
Spatial and temporal solitons are at the core of many physical, geological, biological, transmission and information
processing and other problems. However, in most cases we have focused on their steady behavior, and therefore on
homogeneous media and their single soliton eigenvalues spectrum. This has been done even in the case of an all optical
simultaneous loss and amplification, where we have assumed stability of those eigenvalues. However, the transient
behavior has received little attention, often disregarded under a generic pulse reshaping or experimentally diafragmed as
often occurs in large amplifiers. But such transient behavior can be frozen in a periodic nonhomogenous media, tandems,
where such behavior corresponds to the soliton convergence in each tandem media, producing a regular but not steady
behavior. We discuss the resonant pulse propagation in a two level atom media tandem, described by a real convergence
and a Kerr intensity dependent nonlinearity, described by a complex convergence.
Metallic nanoparticles, of a few nanometers radii, show nonlinearities that are
the object of experimental and theoretical studies, in particular in the framework of
composites. A quantum mechanical analysis of such structures predict a Kerr type
nonlinearity, however quite a recent publication on a classical approach has shown
that a classical metallic nanoparticles composite shows a nonlinearity proportional
to the electric field amplitude, not to the intensity as is in the Kerr case. The
capability of filling up the core of a piece fiber with such composites open the
possibility of preparing long enough pieces of fiber with such a composite as well
as the straightforward drawing of a fiber doped with nanoparticles. In this work we
carry on the numerical simulation on such class of fibers, with the specific aim of
looking at the corresponding soliton propagation in an optical fiber with a core
doped metal nanoparticles.
This paper deals with the non-linear parametric effects on both space charge waves (with phase velocity equal to the
electron drift velocity) and electromagnetic waves (with phase velocity equal to c1 , where c is the permittivity) in GaAs
semiconductors. If an external electric field is applied, a negative differential conductivity is obtained. Under these
conditions, the electron velocity is a function of the electric field, which is given by E =E0 + E , where E0 is the constant
part and is the variable part. The analysis of the parametric interaction of the waves in the GaAs semiconductor is realized
considering both the Maxwell's equations and the velocity function. The one-dimensional model and the axis z, as the
spreading wave direction, are chosen. The analyses of instabilities are realized -by using the Blombergen's Method. The
instability efficiency is determined by the velocity, V0, the differential mobility, jiD; and the non-linear parameter, VD;by
means of the temperature model of the Gunn Effect. The efficiency is good if the interaction parameters As and as, which
are obtained from the system formed by the Maxwell's equations and the velocity function, are optimal. At the critical field
value, Ecrit, the mobility changes its sign and becomes negative, as a result, there are obtained non-linear and linear
parametric instabilities of the interactions at fields E2Ecrjt. The nonlinear parameter Vd obtains a maximum at the optimal
value of electric field, where all linear processes are very effective.
Epitaxial metastable (GaAs)1x(Ge2)x thin films have been grown on GaAs(100) in a rf planar magnetron sputtering system
(MS), without As overpressure, throughout most of the full compositional x range. The structural and compositional
properties are investigated by high resolution x-ray diffraction (HRXRD) and secondary ion mass spectrometry (SIMS). The
SIMS depth profiles demonstrate good homogeneity of Ge concentration for all the samples. HRXRD measurements show
that the lattice constant has a nonlinear dependence on the concentration x and that a transition between zmc-blende and
diamond crystal structures occurs at x 0.35. The existence of interfacial layers and the interference between the scattered
amplitudes for the epilayer and substrate are considered negligible effects on the lattice parameter determination, and
computer simulations confirm this assumption. We propose, from SIMS, HRXRD measurements and X-ray profiles
simulations, that the lattice constant behavior is influenced by the resultant As/Ga ratio in the film.
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