N. N. Rozanov

Two-dimensional solitons in B-class lasers with saturable absorption

Localized radiation structures under conditions of a semiconductor laser with saturable absorption and a vertical cavity with a large Fresnel number are analyzed numerically and analytically. The boundaries of the region of existence and stability of transversely two-dimensional solitions, the boundary of transition to a moving state, and the boundary of the Andronov-Hopf bifurcation are found. Stable fundamental and vortical (topologically charged) solitons are obtained in a range of relaxation times of the nonlinearities of the media up to 400 lifetimes of a photon in the cavity. These solitons were obtained under the condition that the chosen medium with saturable absorption has a slower response than the active medium of the laser. Otherwise, a rapidly moving solition is formed, which is similar in its properties to a combustion wave. Properties of such a rapid motion along the aperture can be useful for optical data processing.

Nanosized discrete dissipative solitons in resonantly excited molecular J-aggregates

The resonant excitation of a linear oriented molecular chain simulated by a system of two-level schemes interacting through radiation has been analyzed. The regimes of modulation instability, switching waves, and dissipative solitons whose sizes for J-aggregates can reach about 1 nm have been revealed.

Dissipative discrete spatial optical solitons in a system of coupled optical fibers with the Kerr and resonance nonlinearities

The propagation of monochromatic radiation in a system of weakly coupled single-mode optical fibers with saturable amplification and absorption and Kerr nonlinearity of the refractive index is analyzed. Conditions of stability and bistability of plane-wave regimes are determined. Discrete dissipative optical solitons are found and their stability is studied. The hysteresis dependences of the peak intensity of the discrete solitons on the value of the Kerr nonlinearity and the input beam intensity are demonstrated. The numerical estimates of the parameters of the spatial dissipative discrete solitons are presented.

Dissipative vector Bragg solitons in a birefringent optical fiber

Motionless dissipative vector solitons are found numerically in a birefringent polarization-conserving optical fiber with a longitudinal Bragg grating and nonlinear amplification and absorption in the polarization capture regime. It is shown that dissipative vector Bragg solitons exist and are stable even if the birefringence is comparatively strong.

Clusters of three-dimensional laser solitons and their collisions

A new class of clusters of three-dimensional dissipative inphase-and antiphase-coupled solitons is numerically found in a laser system with a saturable absorber. The orientation of clusters and their motion depend on the symmetry of spatiotemporal characteristic of the system and on the symmetry of arrangement of solitons in the cluster. An example of a nonplanar (spiral-like) trajectory of the center of a seven-soliton cluster possessing no symmetry elements is demonstrated. Collisions of moving soliton clusters, including those accompanied by exchange of solitons between clusters, are studied. Experimentally, three-dimensional dissipative optical solitons can be realized in a laser amplifier with a saturable absorber or in an extended resonator filled with a medium with nonlinear gain and absorption.

About the Regime of Unidirectional Propagation of Radiation in Nonlinear Media

The generation of counterpropagating waves with low frequencies by pump copropagating waves in a weakly nonlinear medium is analyzed. The generation is shown to be efficient in the presence of intervals with anomalous and normal dispersion in the spectrum. Under these conditions, the approximation of unidirectional propagation, which is widely used in the literature, is incorrect and the nonlinear propagation of radiation should be described by the full wave equation.

The doppler frequency shift caused by the inhomogeneities of a medium induced by pulses of intense laser radiation

Self-reflection of pulses of intense laser radiation from an inhomogeneity induced by them in a medium with fast optical nonlinearity is analyzed. The reflected radiation is characterized by a considerable Doppler shift and by a signal magnitude that is sufficient for experimental detection.

Self-broadening of space-time spectra of few-cycle pulses in dielectric media

The nonparaxial dynamics of spectra of pulses comprising a few cycles of a light field is analyzed in transparent nonlinear media with dispersion. It is shown that the inhomogeneous self-broadening of the time spectrum of a pulse proceeds more effectively into the blue region at all spatial frequencies. A decrease in the energy in the central part of the time spectrum is realized mainly at high spatial frequencies.

On reflection of radiation from moving objects

An analytical expression for the field reflected from a nonuniformity of the velocity of a moving medium is obtained. Specific features of the reflected radiation depending on the velocity and sizes of the non-uniformity domain and on the angle of incidence of radiation relative to the direction of motion are studied. The feasibility of experimental detection of the reflected radiation is demonstrated.

Curvilinear Motion of Laser Soliton Complexes

Conditions under which the center of inertia of stable complexes of dissipative optical solitons moves curvilinearly have been determined. Such a character of the motion of dissipative structures is caused by asymmetry in the distribution of the intensity and energy fluxes, and it is pronounced for laser solitons with strong interaction. The results of the numerical simulation of these complexes in the model of surface emitting lasers or laser amplifiers with saturated amplification and absorption are presented. Such complexes may be observed in various spatially distributed nonlinear dissipative systems, in particular, in the form of discrete solitons.