Biomedical subjects

M Kolesik

Publications and source records attributed to M Kolesik.

5 recordsLinked to original sources

PubMed2003

Physical factors limiting the spectral extent and band gap dependence of supercontinuum generation.

Based on simulations of femtosecond pulse propagation in water we elucidate the physical factors that limit the attainable spectral extent of supercontinuum generation in bulk media. In contrast to the standard scenario, where arrest of self-focusing collapse by multiphoton absorption and plasma defocusing are viewed as imposing a limit to supercontinuum broadening, we show that linear chromatic dispersion also plays a major role. This insight provides an intuitive explanation of the observed band gap dependence of the attainable supercontinuum generation in condensed media.

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PubMed2003

Relevance of symmetry for the synchronization of chaotic optical systems and the related Lang-Kobayashi model limitations.

Synchronization of chaotic semiconductor lasers has now been demonstrated experimentally in a variety of coupling schemes. Coupling methods include configurations where the transmitter laser system is itself chaotic and drives a receiver system, both lasers are individually chaotic, and both lasers induce the chaos through mutual coupling. The dynamics for each of these scenarios is in many cases adequately captured by the Lang-Kobayashi rate equation model. Such a simplified model, however, ignores fundamental aspects of the laser dynamics, such as the frequency and carrier density material susceptibility dependence, spatial hole burning effects, proper boundary conditions, and the fact that lasers may exhibit pronounced multilongitudinal dynamic behavior with and without the presence of a weak external feedback or injection. The model also cannot distinguish between many of the possible coupling geometries realizable in experiments. Using an interactive simulator based on the rigorous microscopic description of the light-matter interaction, we explore the unidirectionally coupled configuration, the relevance of symmetry for the synchronization achieved between two identical lasers, and the differences that arise when the traditional analysis through the Lang-Kobayashi model is compared to the full nonlinear partial differential equation model results.

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PubMed2002

Unidirectional optical pulse propagation equation.

A unidirectional optical pulse propagation equation, derived directly from Maxwell's equations, provides a seamless transition between various nonlinear envelope equations in the literature and the full vector Maxwell's equations. The equation is illustrated in the context of supercontinuum generation in air and is compared to a recent scalar model of Brabec and Krausz. Fully vectorial aspects of the model are illustrated in the context of extreme focusing of a femtosecond pulse.

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PubMed2002

Microstructure and velocity of field-driven solid-on-solid interfaces: analytic approximations and numerical results.

The local structure of a solid-on-solid interface in a two-dimensional kinetic Ising ferromagnet or attractive lattice-gas model with single-spin-flip Glauber dynamics, which is driven far from equilibrium by an applied field or chemical potential, is studied by an analytic mean-field, nonlinear-response theory [P. A. Rikvold and M. Kolesik, J. Stat. Phys. 100, 377 (2000)], and by dynamic Monte Carlo simulations. The probability density of the height of an individual step in the surface is obtained, both analytically and by simulation. The width of the probability density is found to increase dramatically with the magnitude of the applied field, with close agreement between the theoretical predictions and the simulation results. Excellent agreement between theory and simulations is also found for the field dependence and anisotropy of the interface velocity. The joint distribution of nearest-neighbor step heights is obtained by simulation. It shows increasing correlations with increasing field, similar to the skewness observed in other examples of growing surfaces.

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PubMed2001

Polarization dynamics of femtosecond pulses propagating in air.

Polarization dynamics of femtosecond light pulses propagating in air is studied by computer simulation. A rich variety of dynamics is found that depends on the initial polarization state and power of the pulse. Effects of polarization on the plasma and supercontinuum generation are also discussed.

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