Yuri A. Shpolyanskiy

Self-action of femtosecond pulses with continuum spectrum

On the basis of the analysis of the wave equations for an electrical field of radiation and without use of slowly varying envelope approximation the self-action of femtosecond light pulses in transparent media is investigated. The results of numerical simulation of spectral supercontinuum evolution, accompanying temporary broadening of intensive pulses with a spectrum in the range of normal group dispersion of medium both with only electronic nonlinearity, and with simultaneous electronic and electronic-vibrational nonlinearities are presented. The opportunity of compression of pulses with supercontinuum spectrum in light formations consisting of one cycle of an electric field is predicted. It is shown that spectral superbroadening of the elliptically polarized radiation is accompanied by nonuniform rotation of a polarization ellipse.

Theory of spectral supercontinuum generation in microstructure fibers

We investigate an extremely complex mechanism of spectral supercontinuum generation at the propagation of intensive femtosecond laser pulses in microstructure (photonic crystal) fibers beyond the slowly-varying envelope approximation. We discuss and compare theoretical approaches grounded on the considerations of field and spectral evolution of the pulses. We present new nonlinear spectral equation, first-order in propagation coordinate, applicable for the study of femtosecond supercontinuum generation in microstructure fiber with arbitrary linear dispersion. We demonstrate a very good agreement to independently published experimental data found in numerical simulations. We study formation and evolution of few-cycle solitary waves under the effects of Kerr and Raman nonlinearities.

Nonlinear reflection of extremely short light pulses

The reflection of intense laser pulses consisting only of several light field cycles from nonlinear, isotropic and transparent dielectric media is theoretically investigated. It is shown, that the spectrum of the reflected pulse is enriched by odd harmonics and at close linear refraction indices of bordering media the duration of the reflected pulse can become less significant than the duration of incident pulse. It is shown, that the intense refracted wave has a strongly asymmetrically broadened spectrum in nonlinear medium.

Nonlinear reflection of few-cycle light pulses off a bloomed dielectric interface

Fresnel formula for the normal incidence of light is generalized to the case of reflection of broad-spectrum radiation off a dielectric with nonresonant dispersion and nonlinearity. Considering reflection of few-cycle light pulses off a bloomed dielectric interface, we show that self-division of a reflected pulse can occur at low incident intensities, while substantial modification of the pulse shape including self-compression is possible at higher intensities.

Nonlinear optical problems of light pulses with one and more cycles

The equations describing the propagation dynamics of optical pulses consisting of several electrical field cycles and pulses with spectrum bandwidth comparable with the central frequency are presented. The numerical simulation of nonlinear optical phenomena observed in isotropic media with pumping by the pulses with the spectrum in area of the normal group dispersion is carried out. The spectrum ultrabroadening of a short pulse with the temporal broadening, the self-induced changes of the pulse polarization, the simultaneous generation of several Stokes, anti-Stokes components, the third harmonic and sum and difference frequencies generation with self-phase and cross- phase modulation are considered.

Features of spectrum supercontinuum generation by intensive femtosecond laser pulses in transparent optical media propagation

The expirements of recent years show that by intensive femtosecond laser pulses propagation in transparent optical media the radiation which spectral width comparable with its central frequency (spectrum supercontinuum generation phenomenon) is observed.

Self-induced changes in the polarization of pulses of a few oscillations duration in isotropic dielectric media

The new wave equation describing nonlinear propagation in isotropic dielectric media of any polarization optical pulses containing only a few oscillations of light field has been obtained. The polarization self-action of such extremely short pulses is shown to be in change of orientation of their electrical field amplitude vector along the direction of propagation proportional to a square of a field amplitude and the rotate velocity of amplitude vector.