Nikolai N. Rozanov

Formation of soliton-like light beams in an aqueous suspension of polystyrene particles

A Kerr nonlinear medium consisting of an aqueous suspension of dielectric nanoparticles is used for the observation of continuous self-focusing of laser light. The minimum width of the soliton-like beam is measured in relation to the radiation power and the particle concentration. The possibilities of maximum narrowing of the beam in such a medium are discussed.

Spatial soliton-like structures in a thin-film system with a transverse photonic crystal in the feedback loop

The problem of existence and stability of soliton-like structures in a system consisting of a thin layer with resonance nonlinearity, a feedback mirror, and a photonic crystal located between them is studied. It is shown that, depending on the parameters of the photonic crystal, its presence can lead both to a change in the background on which localized structures are excited and to an increase in the interval of test pulse amplitudes necessary for the excitation of these structures.

Pulsating solitons in a laser with relaxation of gain and saturable absorption

Results of numerical simulation of the formation of pulsating solitons in a laser with relaxation of gain and saturable absorption are presented. The regions of relaxation parameters are found in which stationary pulsating solitons and solitons with strong modulation of the pulsation amplitude are observed. Examples of multiple subsequent doubling of the oscillation period, caused by changing relaxation parameters, are presented.

Conditions for the existence of laser bullets

Conditions for the existence of completely localized three-dimensional dissipative laser solitons—“laser bullets” in a medium with nonlinear amplification and absorption and frequency dispersion are studied. Solitons with different profiles are considered and the regions of their stable existence are found. The stability of spherical solitons is studied as a function of frequency mismatch of amplification and absorption lines by the method of direct numerical simulation.

Nonstationary multivortex and fissionable soliton-like structures of laser radiation

New types of nonstationary soliton-like structures of laser radiation were found in the mean field approximation by numerical simulation of a class A wide-aperture laser with saturable absorption. In the absence of frequency detunings, multivortex (with several wavefront dislocations distributed over the aperture) asymmetric rotating solitons were revealed, which can be interpreted as strongly coupled states of symmetric laser solitons with topological charges coinciding or differing in sign. In the presence of detunings between the central frequencies of the gain and absorption profiles and the frequency of the cavity mode, “biosoliton” regimes were obtained, which are characterized by the expansion of the initial localized structure and the periodic separation from it of fragments having similar dynamics.

Dissipative extremely short localized structures of radiation

Sets of steady-state localized temporal structures of radiation with a duration comparable with the period corresponding to the frequency of atomic transitions are found for a medium consisting of active (with a pump) and passive (without a pump) atoms with homogeneous broadening. The velocity of motion of these structures takes discrete values depending on the number of field spikes and the number of oscillations of the polarization of the active and passive atoms within the intervals between the field spikes.

Incoherent weak coupling of laser solitons

A coupled state of a pair of spatial laser solitons with different topological charges in a wide-aperture class-A laser with saturable absorption was found by numerical simulation. In view of a difference in the frequencies of the individual solitons, periodic (with a period corresponding to the frequency difference) weak pulsations of the shape of the solitons and of the spacing between them take place, but the rotation of the pair and the motion of its center of inertia were not revealed.

Moving and Oscillating Transversely One-Dimensional Laser Solitons

Transversely one-dimensional moving and oscillating solitons in a wide-aperture laser with saturable absorber with fast (inertialess) nonlinearity are found by numerical simulation. The regions of existence of such solitons and of their complexes are presented.

Dissipative solitons in active Bragg gratings

Motionless and moving bright dissipative solitons in an optical fiber with a Bragg grating and non-linear amplification and absorption are found numerically and studied. These solitons form a one-parameter family whose parameter—the soliton velocity—can continuously change in a certain range. The presence of saturation of the nonlinearity is necessary for stability of such solitons. Neglect of saturation of the cubic-in-field polarization of the medium results in the instability of the possible localized structures.

Bistability of Material Waves in an Atomic Bose-Einstein Condensate in a Magnetic Interferometer

It is shown theoretically that, upon filling a ring cavity (a loop magnetic waveguide) with an atomic Bose-Einstein condensate (BEC), a hysteresis dependence of the atomic number density inside the cavity on the atomic flux introduced into the cavity from the outside appears. Main parameters of the measuring system being proposed are determined: the reflectance of the magnetic mirror through which the condensate is introduced, the length of the ring cavity, and the strength of the constant magnetic field governing the BEC velocity in the cavity.