Diffraction of ultrashort optical pulses from circularly symmetric binary phase gratings.

The complete spatiotemporal characterization of the diffracted field of ultrashort pulses after passing through circularly symmetric binary phase diffraction gratings is carried out. The complex field is registered at different planes behind the gratings with an ultrashort-pulse measurement technique called SEA TADPOLE. Numerical simulations based on scalar diffraction theory are compared with the measurements.

Evolution of subcycle pulses in nonparaxial Gaussian beams.

A simple but exact treatment of spatiotemporal behavior of ultrawideband pulses under an arbitrarily tight focusing is developed. The model makes use of the oblate spheroidal coordinate system to represent free scalar field as if generated by a point-like source-and-sink pair placed at a complex location. The results, illustrated by animated 3D plots, demonstrate characteristic temporal reshaping of the pulses in the course of propagation through the focus, which is a spectacular manifestation of the Gouy phase shift. It is shown that the salient features of the reshaping, which were recently established for the paraxial limit, remain valid beyond it. The treatment is particularly applicable to an ultrawideband isodiffracting ultrashort terahertz-domain or light pulses in high-aperture resonators, such as microcavities, and it is usable in femto- and attosecond optics in general.

Optical generation of focus wave modes.

Localized wave solutions of free-space wave equation can be used in numerous applications where the localized transmission of electromagnetic energy is of major importance. However, an optical implementation of localized wave fields has not been accomplished yet, except for an ultrashort version of the Bessel beams or the so called Bessel-X pulses. We propose an approach to constructing realizable optical schemes for generation of localized wave fields. We show that wavelength dispersion of the cone angle of axicons and circular diffraction gratings can be used to generate good approximation to focus wave modes.

Demonstration of the Bessel-X pulse propagating with strong lateral and longitudinal localization in a dispersive medium.

We report experiments on ultrashort pulses that maintain their strong lateral and longitudinal localization in a bulk linear highly dispersive medium. The diameter of the central peak and the temporal width of the field autocorrelation function of the pulses were 20mum and 210 fs, respectively, and the spatiotemporal structure was preserved in the course of 7-cm propagation in the sample. The pulses were obtained with a computer hologram designed for generating the Bessel beam and can be applied in femtosecond laser optics.

Suppression of temporal spread of ultrashort pulses in dispersive media by Bessel beam generators.

Linear-optical solutions to the problem of temporal broadening of ultrashort light pulses propagating in air or in solid optical samples are proposed and tested by computer simulations. A special holographic-element setup is analyzed in detail.

Age- and sex-related differences in lipid peroxidation of mouse cardiac and skeletal muscles.

1. The purpose of the present study was to characterize age- and sex-related changes in lipid peroxidation capacities and enzymatic antioxidants of cardiac and skeletal muscles in NMRI-mice (Mus musculus). 2. Lipid peroxidation rates (unstimulated and enzymatic/iron-stimulated) strongly decreased in skeletal muscle during ageing. 3. Unstimulated lipid peroxidation rate but not that of stimulated, also decreased in cardiac muscle. 4. The total level of Fe2+/ascorbate-stimulated non-enzymatic lipid peroxidation was not, however, affected by ageing. 5. The activity of catalase slightly increased in cardiac muscle and that of glutathione peroxidase in skeletal muscle during ageing. 6. Unstimulated lipid peroxidation rate was significantly higher in the skeletal muscle of male than female mice. 7. Correspondingly, the Fe2+/ascorbate-stimulated lipid peroxidation capacities of microsomal and mitochondrial fractions of skeletal muscle were significantly higher in male mice. 8. The activity of glutathione peroxidase as well as the concentration of lipofuscin were higher in the cardiac muscles of female than male mice.