RESUMO
Laser-induced self-organization of regular nanoscale layered patterns in fused silica is investigated using spectroscopy and microscopy methods, revealing a high presence of stable broken oxygen bonds. Longitudinal traces are then generated by replicating static irradiation structures where the nanoscale modulation can cover partially or completely the photoinscribed traces. The resulting birefringence, the observed anisotropic light scattering properties, and the capacity to write and erase modulated patterns can be used in designing bulk polarization sensitive devices. Various laser-induced structures with optical properties combining guiding, scattering, and polarization sensitivity are reported. The attached polarization functions were evaluated as a function of the fill factor of the nanostructured domains. The polarization sensitivity allows particular light propagation and confinement properties in three dimensional structures.
RESUMO
The problem of the decay of an initial discontinuity (the Riemann problem) is studied for a substance with abnormal properties when the rarefaction waves get a shock form, whereas the compression waves become nonsharp with the width proportional to the distance traveled. Such a situation is inherent to matter in a near-critical thermodynamic state and is also met in many other physical systems. The behavior of pressure jumps is compared for the van der Waals equation of state and for its more realistic three-parametric modification. It is shown that the evolution of the rarefaction and compression waves is strongly dependent on the value of the fundamental gasdynamic derivative determined by the equation of state. We demonstrate that for some substances with abnormal properties both rarefaction and compression waves can keep a shocklike form for a long period of time after discontinuity decay.
