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Photonic crystal fibers have been the subject of several studies for potential applications in areas such as telecommunications, sensing, metrology, biology, medicine and spectroscopy. These fibers have a number of unique features owing to their geometric structure, which consists of a matrix of regular holes that travels along its longitudinal axis. This design allows the selective insertion of materials such as gas and liquids, which interact efficiently with the guided modes. The insertion of materials can also be explored to introduce a new degree of freedom to control the properties of waveguide, by modifying modal features such as nonlinear coefficient and dispersion. Such control may, in some cases, contribute to increase the efficiency of nonlinear effects, enabling the creation of a supercontinumm spectrum. In this work we compare results obtained both experimentally and numerically of supercontinuum generation in a distilled water-core photonic crystal fiber. The results indicate the importance of setting the pump close to the zero dispersion region of the material so that a broad spectrum can be obtained. Improved agreement between experiments and simulations requires a better degree of experimental detail to be incorporated into the theoretical model, which will be the objective of future studies and work. [ABSTRACT FROM AUTHOR]

In this paper, on the basis of numerical calculations and results of processing of the data of field experiments, quantitative estimates of the spectral broadening of the initial sounding seismic oscillations are presented. The estimates were obtained as a result of vibroseismic sounding of fractured dilatancy media typical for seismically and volcanically dangerous zones. The authors' idea about the applicability of the parameters of wave field nonlinearity in the form of possible prognostic characteristics of the earthquake-volcano source development process is justified. [ABSTRACT FROM AUTHOR]

The results of experimental confirmation of the theoretical studies of the nonlinear acoustic phenomena in the atmosphere are presented. Riemann's solution of the nonlinear Burgers equation was experimentally supported. A rather good agreement was obtained between the experimental and calculated values of the maximum spectrum frequency of acoustic signals corresponding to different reflection heights in the middle atmosphere, which confirms the validity of the use of the nonlinear Burgers equation in estimating nonlinear variations in the length of acoustic pulses propagating to the upper atmospheric layers. [ABSTRACT FROM AUTHOR]

Plasma radiation plays the determining role in temperature balance, equilibrium and stability of plasmas at the edge of fusion devices. The differences in properties of radiative plasmas and pure hydrogen ones are significant. The sound branch is split into two branches, i.e. fast and slow sounds. They may be destabilize by radiation and stabilized by internal relative motion of species. The basic properties of radiative plasmas are discussed in the current presentation. Radiation of multi-electron impurity ions is significant, even if the impurity concentration is small. It depends strongly on the Impurity Distribution Over Ionization States (IDOIS). One can find many interesting effects taking into account the finite relaxation time of IDOIS and thermal forces. In particular, the anomalous sound damping due to the internal friction, decompression shocks, slow thermal waves, and self-sustained thermal oscillation are discussed in the current presentation. Opacity effects also are discussed in the current presentation. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

We report size-dependent optical limiting response of YCrO3 nanosystems upon illumination by nanosecond laser pulses at 532 nm. The limiting properties were investigated using the open aperture z-scan technique. Three-photon absorption coefficient is found to increase with particle size within the range of our investigations. We propose that the obtained nonlinearity is caused by two photon absorption, followed by excited state absorption. [ABSTRACT FROM AUTHOR]