Possible scenarios of high-intense vortex (and Gaussian) pulsed beam propagation in Kerr media and light bullet (LB) formation conditions are considered. The system of modified nonlinear Schroedinger equation for the complex envelope of the electric field and kinetic equation for the electron plasma density is exploited. Two-scale variational analysis is combined with direct numerical simulations based on finite-difference methods. Hamiltonian approach allows to reveal LB formation conditions. It is shown that the LB parameters correspond to minimum of potential energy when the whole balance of competing processes occurs. Numerical experiment confirms the results obtained on the base of variational analysis, demonstrating at the same time softer conditions for LB formation. It is emphasized that the linear and nonlinear dynamics of spatial and temporal radii obey the coupled oscillator theory.
We search for efficient schemes of second and terahertz harmonic generation in nanocomposites consisted of metal-oxide semiconductor quantum dots incorporated into a dielectric matrix, when the quantum dots are in resonance and the dielectric matrix is out of resonance with femtosecond light pulse. It’s established that large efficiency of frequency up-conversion is possible to attain, which may be for the optimal quantum dot concentration in above mentioned nanocomposites by 70% higher than in pure nonlinear dielectric matrix.
Dynamics of powerful femtosecond singular-phase pulsed beams in a dielectric medium under the ionization
conditions is analyzed numerically. The multiphoton ionization is revealed to contribute to the stable (quasi-soliton)
regime of pulse propagation over distances exceeding five diffraction length. Use of the singular beams allows one to
reach the larger densities of the light field and generated plasma.
This paper is devoted to growth and doping of semiconductor photorefractive cadmium telluride <i>(CdTe)</i> crystals as well as to the investigation into their spectroscopic and non-linear optical properties. The crystals are doped with vanadium, iron, and titanium. Two methods have been used for the production of doped crystals: diffused post-growth doping and growth of doped crystals from melt. Non-linear optical properties of the samples were studied at a wavelength of 1.06 μm for a four-wave mixing geometry and 1.54 μm for a two beam coupling. Maximum 2% diffraction efficiency at 1.06 μm was revealed with the convergence angle of light beams approximating 8" for the grating period of 7 μm. In this case the dynamic grating lifetime was found to be about 0.2 μs. Under beam coupling at ~ 1.5 μm, the conditions of maximum gain (0.7 cm<sup>-1</sup>) were observed in the experiment for a minimum grating period of 1 μm; and the gain could be slightly enhanced by application of a dc electric field (~ 2 kV/cm) up to 40%.
Supercontinuum generation in planar rib waveguides promising for numerous applications is predicted theoretically. Its physical origin is connected with radiation and fission of higher-order solitons in anomalous dispersion region caused by the modification of dispersion by the waveguide contribution.
The effect that may be exerted by an interatomic near dipole-dipole interaction upon optical transient processes in dense resonance media is analyzed. The behavior of the macroscopic polarization after a one-pulse excitation of a dense ensemble of two-level atoms is considered. It is shown that the free polarization signal is of oscillatory nature, with the oscillation frequency varying in time and being dependent on the dipole-dipole interaction constant, the intensity and duration of the exciting pulse, and the detuning of its carrier frequency from the resonance. The free polarization signal decay, which depends on the magnitude and sign of the sum of the detuning of the exciting pulse carrier frequency from the resonance and the Lorentz frequency, may obey either a power or an exponential law. The signal decay rate is determined not only by the inhomogeneous broadening, but also by the ratio of the above parameters. The peculiarities of echo-responses under one- or two-pulse excitation conditions are studied.
The intrinsic optical bistability, soliton formation, and transient phenomena such as the free polarization decay and photon echo in dense resonant media are investigated, taking into account the short-range dipole-dipole interaction of atoms.
KEYWORDS: Diffraction, Modulation, Chemical species, Distortion, Wave propagation, Nonlinear optics, Solid state electronics, Pulsed laser operation, Commercial off the shelf technology, Personal protective equipment
The primary photon echo signal excited by two non-collinear pulses in optically dense media with extreme inhomogeneous broadening is investigated theoretically and numerically. Non-linear evolution of both echo exciting pulses and echo response during propagation is taken into account. Red frequency shift of the primary photon echo is predicted. The influence of pulse transformation on the echo time delay is analyzed.
The peculiarities of the photon echo excitation by two non- collinear pulses in optically dense media with extreme inhomogeneous broadening are investigated theoretically and numerically. Non-linear pulse evolution during propagation is taken into account. Red frequency shift of the primary photon echo signal is predicted. The influence of pulse transformation on the echo time delay is analyzed.
The effect of phase-conjugate feedback on the semiconductor laser dynamics is considered theoretically. The optical feedback is realized on the base of the intracavity four-wave mixing in the Cs vapors.
Multiple photon echo generation process in extended crystals is investigated taking into account both the contribution of irreversible relaxation during whole excitation time and propagation effects caused by the resonant medium influence on the exciting pulse sequence and echo-responses.
Nonstationary energy exchange between reading pulse and reconstructed waves is analyzed as a function of their energy and spectral characteristics, as well as of their small-scale instability. It is shown that for small values of spatial frequencies, (kappa) <SUB>1</SUB>, in transverse structure of object wave, phase-locking of reconstructed waves is observed which stabilizes the energy exchange. At the same time the efficiency of wavefront reconstruction is substantially influenced by the instability of the reading pulse with respect to small-scale perturbations of its transverse structure. With increasing (kappa) <SUB>1</SUB> the above process depends also on the effect of phase accumulation. In optically dense media the suppression of instability is not observed, but there are special conditions defined by the value and sign of detuning of reference pulse carrier frequency from resonance, under which this instability grows slowly.