N. V. Ustinov

Propagation of vector solitons in a quasi-resonant medium with stark deformation of quantum states

The nonlinear dynamics of a vector two-component optical pulse propagating in quasi-resonance conditions in a medium of nonsymmetric quantum objects is investigated for Stark splitting of quantum energy levels by an external electric field. We consider the case when the ordinary component of the optical pulse induces σ transitions, while the extraordinary component induces the π transition and shifts the frequencies of the allowed transitions due to the dynamic Stark effect. It is found that under Zakharov-Benney resonance conditions, the propagation of the optical pulse is accompanied by generation of an electromagnetic pulse in the terahertz band and is described by the vector generalization of the nonlinear Yajima-Oikawa system. It is shown that this system (as well as its formal generalization with an arbitrary number of optical components) is integrable by the inverse scattering transformation method. The corresponding Darboux transformations are found for obtaining multisoliton solutions. The influence of transverse effects on the propagation of vector solitons is investigated. The conditions under which transverse dynamics leads to self-focusing (defocusing) of solitons are determined.

Resonance-parametric mechanism of optical rectification and high harmonic generation

The generation of zero and high-order harmonics in the spectrum of a laser pulse propagating through a medium containing quantum particles whose constant resonance transition dipole moment is nonzero is studied theoretically. The consideration is performed in the approximation of slowly varying envelopes modified for the case of the medium with the nonzero permanent dipole moment. It is shown that this modification requires consideration of antiresonance terms, in particular, the Bloch-Siegert shift in equations. The conditions are revealed for the efficient optical rectification and excitation of the second harmonic at a quasi-monochromatic signal applied to the medium.

Propagation of Picosecond Transverse Acoustic Pulses in a Kramers Doublet System

Propagation of extremely short transverse-strain pulses is studied in a low-temperature crystal containing paramagnetic impurities with an effective spin S = 1/2 in Voigt geometry. It is shown that various types of acoustic solitons can form due to the spin-acoustic interaction between elastic-field components.

New kinds of acoustic solitons

We find that the modified sine-Gordon equation belonging to the class of the soliton equations describes the propagation of extremely short transverse acoustic pulses through the low-temperature crystal containing paramagnetic impurities with effective spin S=1/2 in the Voigt geometry case. The features of nonlinear dynamics of strain field and effective spins, which correspond to the different kinds of acoustic solitons, are studied.

Acoustic rectification and generation of the second hypersonic harmonic in the resonant parametric soliton regime

A resonant parametric mechanism of generation of the zeroth and second harmonics of acoustic pulses propagating in a crystal involving resonance Zeeman transitions is proposed. The analysis performed has made it possible to determine the conditions for the effective acoustic rectification and excitation of the second harmonics in the resonant parametric soliton regime. The advantage of the proposed mechanism of acoustic harmonic generation over the conventional mechanism associated with the acoustic anharmonicity is that the degree of conversion is controlled by a change in the external magnetic field strength and the direction of propagation of the input pulse.

Self-induced transparency in an optically dense medium of nonsymmetric quantum objects

This paper discusses the soliton propagation regime of a laser pulse consisting of optical ordinary and terahertz extraordinary components in optically uniaxial media that contain nonsymmetrical resonance nanoobjects of the type of quantum filaments. The treatment takes into account dipole-dipole interaction between the nanoobjects. The conditions are explained under which a terahertz pulse can be efficiently generated when a near-IR optical signal is supplied to the input of the medium. It is shown that this generation process is accompanied by displacement of the spectrum of the optical component into the red region, with this displacement increasing as the pulse width becomes shorter.