The study of nonlinear photonics crystals is quite complex and cumbersome, because of their inherent architectural complexity and, in addition, because of the nonlinearity that couples propagating and counterpropagating waves. However, they are quite attractive because of their potential capabilities, and that has lead to use different approximated methods. In a one dimensional stack, it has been successfully demonstrated that they show switching, bistability and chirping as nonlinear characteristics. Band gap solitons are a well established feature of the coupled wave equations. We have extended a method that have previously shown its success for a stack with a Kerr nonlinearity, to a much more complex structure such as an omniguide fiber, as part of our suggestion that such method could be applied to numerical or analytical methods as long as the linear solution were available. Such a restriction, hinder our ability of
getting analytical solution beyond their enabling approximations, however, it is completely adequate for the purpose of to develop devices. A comparative numerical analysis of a one dimensional photonic crystal and an omniguide fiber, made of a dielectric
and stratified linear and nonlinear media, has been carried out. They were considered as multilayer arrangements with a finite numbers of periods: linear-linear, nonlinear-linear and nonlinear- nonlinear in order to study and isolate those features. Finally, a comparison of multilayer systems with variations in the diffraction indexes profiles is presented.
Satellite instruments detected two intense decreases of the ozone column values over Europe in November 1996 and November 1999. These low ozone events have been studied using atmospheric data and air parcel trajectory analyses. It was found that both ozone events were accompanied by rapid temperature decreases in the lower stratosphere. The anti-correlation found between total ozone and air parcel height along the air parcels trajectories suggested that the vertical displacement of air contributed significantly to the total ozone and temperature decreases observed. The Azores high-pressure cell over the mid Atlantic region, perturbed the flow in the lower stratosphere, forcing the vertical displacement of air parcels and causing the temperature and total ozone minima observed.
In 1993 a network of differential optical absorption instruments was deployed in Argentina and Chile to study the evolution of the ozone layer in the mid latitudes of South America. The data obtained by this network were compared with the data provided by TOMS (NASA) and TOVS (NOAA) satellite instruments and a good correlation was found. NCAR meteorological data were also used to study in detail the ozone transport in the stratosphere under ozone hole conditions. The data provided by both, the ground based and the spaceborne instruments, revealed that sudden and transient decreases of total ozone column values took place in the mid-latitudes of South America each spring in the period 1993 - 1998. These low ozone events occurred quasi- simultaneously at quite different latitudes. The analysis of potential vorticity maps showed that the lower stratosphere polar vortex penetrated up to approximately latitude 50S in South America every spring since 1993. In addition it was found that the low ozone events were accompanied by sudden air temperature decreases in the lower stratosphere. The computation of the 3D back-trajectories of air parcels showed that air from the surroundings of the ozone hole were transported to the mid latitudes regions. An anti- correlation between air parcels height and total ozone along the trajectory was found suggesting that vertical displacement of air also contributed to the observed ozone and temperature decreases.