Showing papers by "V.P. Kandidov published in 2011"
TL;DR: In this article, the authors studied the evolution of the light field intensity and induced refractive index of a medium upon filamentation of femtosecond laser radiation in air and found that the intensity clamping results from the dynamic balance of optical powers of nonlinear lenses, induced by radiation due to the Kerr nonlinearity of air, and laser plasma produced during photoionisation.
Abstract: We have studied numerically the evolution of the light field intensity and induced refractive index of a medium upon filamentation of femtosecond laser radiation in air. It is shown that the intensity clamping results from the dynamic balance of optical powers of nonlinear lenses, induced by radiation due to the Kerr nonlinearity of air, and laser plasma produced during photoionisation. We have found the relation between the peak values of the light field intensity and the electron density in laser-produced plasma, as well as the transverse sizes of the filament and the plasma channel.
24 citations
TL;DR: In this article, the formation of conical emission of supercontinuum during filamentation of femtosecond laser pulses with central wavelengths in a wide range is studied experimentally, numerically, and analytically.
Abstract: The formation of conical emission of supercontinuum during filamentation of femtosecond laser pulses with central wavelengths in a wide range is studied experimentally, numerically, and analytically. The frequency-angular intensity distribution of the spectral components of conical emission is determined by the interference of supercontinuum emission in a filament of a femtosecond laser pulse. The interference of supercontinuum emission has a general character, exists at different regimes of group velocity dispersion, gives rise to the fine spectral structure after the pulse splitting into subpulses and the formation of a distributed supercontinuum source in an extended filament, and causes the decomposition of the continuous spectrum of conical emission into many high-contrast maxima after pulse refocusing in the filament. In spectroscopic studies with a tunable femtosecond radiation source based on a TOPAS parametric amplifier, we used an original scheme with a wedge fused silica sample. Numerical simulations have been performed using a system of equations of nonlinear-optical interaction of laser radiation under conditions of diffraction, wave nonstationarity, and material dispersion in fused silica. The analytic study is based on the interference model of formation of conical emission by supercontinuum sources moving in a filament.
20 citations
TL;DR: In this article, the supercontinuum (SC) generation during femtosecond laser pulse filamentation with various central wavelengths in fused silica is investigated by numerical solution of nonlinear Schroedinger equation.
Abstract: The Supercontinuum (SC) generation during femtosecond laser pulse filamentation with various central wavelengths
in fused silica is investigated by numerical solution of nonlinear Schroedinger equation. Material dispersion of the
medium is considered due to Sellmeier formula. Nonmonotonic dependence of spectral intensity on wavelength in
anti-Stokes wing for anomalous group velocity dispersion (GVD) region (λ 0 = 1900 nm) was found. There is a local
minimum in SC spectrum from 800 nm to 1200 nm, and there is also a local maximum in SC spectrum from 400 nm
to 700 nm. We suppose such modification of pulse spectrum during filamentation process to be caused by
interference modulation of SC spectrum in presence of anomalous GVD.
1 citations