Characterization methods of nanocomposites consisted of semiconductor metal-oxide quantum dots (Q... more Characterization methods of nanocomposites consisted of semiconductor metal-oxide quantum dots (QD) incorporated into a dielectric matrix have been elaborated on the base of time resolved four-wave mixing and photon echo. Large permanent dipole moment, inherent to QDs under study, local field effect, the QD spatial dispersion and distribution function of the transition dipole moments in QDs are taken into account. New responses at multiple frequencies in directions differed from spatial synchronism conditions of well-known signals have been predicted.
Possible scenarios of high-intense vortex (and Gaussian) pulsed beam propagation in Kerr media an... more 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.
Nonlinear dynamics of high-intensity femtosecond singular pulses in a Kerr medium with group velo... more Nonlinear dynamics of high-intensity femtosecond singular pulses in a Kerr medium with group velocity dispersion (GVD) is analysed using variational and numerical approaches. We study underlying physical processes governing propagation of vortices: diffraction, Kerr self-focusing, defocusing due to photoinduced plasma, and normal/anomalous GVD. Multifoci behaviour of vortices appearing in the medium are revealed. It is shown that the refocusing period depends on both the magnitude and sign of the GVD. The early stages of vortex beam filamentation are described.
In this work, four-wave difference-frequency generation in centrosymmetric media doped with three... more In this work, four-wave difference-frequency generation in centrosymmetric media doped with three-level quantum systems is investigated theoretically. Terahertz radiation generation in the coherent regime of interaction, where the durations of optical pulses are shorter than the relaxation time of coherences induced in two-and one-photon resonant transitions, is analyzed. It is shown that the coherent regime of four-wave frequency mixing enhances the efficiency of radiation generation in the terahertz frequency range. Quantum confined systems (e.g., atoms and molecules in nanoparticles) should be considered as possible media for practical implementation of the method.
We consider the propagation of terahertz (THz) pulses resonant with the lowest rotational levels ... more We consider the propagation of terahertz (THz) pulses resonant with the lowest rotational levels in ammonia vapors at room temperature. We demonstrate a quasisimultonic regime of propagation for two-color THz pulses (their lossless simultaneous propagation with equal group velocities and stable envelopes at finite distances, like coupled solitons). The quasisimultons are formed by two pulses synchronized in time, the first one being intense and two humped with an area multiple of 4π , while the another one is weaker, one humped, and with an area much less than π. Two-and one-humped pulses have equal width and copropagate in ammonia vapor at the same group velocity. Moreover, the larger the dip of the two-hump pulse is, the weaker may be the one-humped pulse. The stability of this coupled state is provided by the fact that the two-humped pulse makes the medium transparent for the one-humped pulse. In its turn, the latter prevents the breakup of the former into separate pulses. It is established as well that a multihumped pulse with an odd or even number of humps and a hyperbolic secant pulse can behave like a simulton. In this case, the area of multihumped pulse equals to 2nπ , where n is the number of humps in the powerful pulse structure.
We predict and numerically study supercontinuum generation extending over almost two octaves in p... more We predict and numerically study supercontinuum generation extending over almost two octaves in planar rib waveguides, with anomalous dispersion at the input wavelength provided by the waveguide contribution. Such planar nonlinear waveguides generating broadband coherent radiation can be intergrated with other components to constitute a building block in intergrated optical circuits.
The spatiotemporal dynamics of a light pulse injected into a dense, resonant medium under near-di... more The spatiotemporal dynamics of a light pulse injected into a dense, resonant medium under near-dipole-dipole interaction conditions is considered. Two regimes for soliton formation are investigated numerically and analytically. The first one occurs if the pulses are much shorter than both relaxation times. In the second, the pulse duration falls between those of the relaxation times and may be regarded as an incoherent one. In the latter case there are conditions in which the dephasing process is suppressed by dipole-dipole interatomic interaction. Not only are one-soliton solutions found but also a powerful pulse splitting into separate solitons is revealed. The regions in which solitons are found have been estimated. The possibility of finding incoherent solitons has been analyzed, with group-velocity dispersion and diffraction of tilted pulses, which are shown to make soliton formation easier, taken into account.
We study the two-pulse photon echo generation process in thin polymer films doped with organic dy... more We study the two-pulse photon echo generation process in thin polymer films doped with organic dye, when the angle between wave vectors of the excitation pulses is varied. The temporal structure as well as the spectral features of the echo-response are analyzed. The evolution from the gradual blue shift of the echo-signal frequency to the red switch of it is predicted.
The peculiarities of the photon echo signal excitation by two non-collinear pulses in optically d... more The peculiarities of the photon echo signal excitation by two non-collinear pulses in optically dense media are investigated theoretically and numerically. Non-linear evolution of both echo response and exciting pulses is taken into account. Red frequency shift of the primary photon echo signal is predicted.
... Khasanov*, TV Smirnova, OM Fedotova Institute of Solid State and Semiconductors Physics, 17 B... more ... Khasanov*, TV Smirnova, OM Fedotova Institute of Solid State and Semiconductors Physics, 17 Bmvki str., Minsk 220 072, Belarus Abstract The accumulated photon echo (APE) excitation process by N pulse pairs ... Fax: (172) 324694; email: [email protected] ...
... O. Kh. Khasanov, TV Smirnova, and OM Fedotova Institute of Solid-State and Semiconductor Phys... more ... O. Kh. Khasanov, TV Smirnova, and OM Fedotova Institute of Solid-State and Semiconductor Physics, Belarussian Academy of Sciences, ul. Brovki 17, Minsk, 220072 Belarus e-mail: ifttpanb%[email protected] Received July 23, 1996 t3 t3' t2 t1' t4 t4' Tc T ττ p t2 ' ...
Long-lived stimulated photon echo (LSPE) excitation by the sequence ofN pulse pairs in optically ... more Long-lived stimulated photon echo (LSPE) excitation by the sequence ofN pulse pairs in optically thick LaF3:Pr 3+ crystals is investigated numerically. Hyperfine structure of the ground and excited states of medium atoms is taken into account. Stable LSPE amplification along the total sample length is realized in the case when the total initial arca of the pulse sequence is larger than the threshold value r~. Cumulative effect depends on the threshold conditions and the crystal length. At measuring medium spectroscopic parameters the large evaluation errors can be introduced due to neglect of light propagation effects.
We search for efficient schemes of second and terahertz harmonic generation in nanocomposites con... more 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.
We consider the propagation of terahertz (THz) pulses resonant with the lowest rotational levels ... more We consider the propagation of terahertz (THz) pulses resonant with the lowest rotational levels in ammonia vapors at room temperature. We demonstrate a quasisimultonic regime of propagation for two-color THz pulses (their lossless simultaneous propagation with equal group velocities and stable envelopes at finite distances, like coupled solitons). The quasisimultons are formed by two pulses synchronized in time, the first one being intense and two humped with an area multiple of 4π , while the another one is weaker, one humped, and with an area much less than π . Two-and one-humped pulses have equal width and copropagate in ammonia vapor at the same group velocity. Moreover, the larger the dip of the two-hump pulse is, the weaker may be the one-humped pulse. The stability of this coupled state is provided by the fact that the two-humped pulse makes the medium transparent for the one-humped pulse. In its turn, the latter prevents the breakup of the former into separate pulses. It is established as well that a multihumped pulse with an odd or even number of humps and a hyperbolic secant pulse can behave like a simulton. In this case, the area of multihumped pulse equals to 2nπ , where n is the number of humps in the powerful pulse structure.
The structure of software for 3D-simulating processes of echo-responses generation in optically d... more The structure of software for 3D-simulating processes of echo-responses generation in optically dense medium is investigated. Complete analysis of the mathematical model realizing various ways of photon echo generation process in extended samples is presented. The contribution of irreversible relaxation during the whole excitation time and propagation effects caused by a nonlinear medium influence on the exciting pulses and echoresponses are taken into account.
The effect of phase-conjugate feedback on the semiconductor laser dynamics is considered theoreti... more 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.
Dynamics of powerful femtosecond singular-phase pulsed beams in a dielectric medium under the ion... more 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.
Characterization methods of nanocomposites consisted of semiconductor metal-oxide quantum dots (Q... more Characterization methods of nanocomposites consisted of semiconductor metal-oxide quantum dots (QD) incorporated into a dielectric matrix have been elaborated on the base of time resolved four-wave mixing and photon echo. Large permanent dipole moment, inherent to QDs under study, local field effect, the QD spatial dispersion and distribution function of the transition dipole moments in QDs are taken into account. New responses at multiple frequencies in directions differed from spatial synchronism conditions of well-known signals have been predicted.
Possible scenarios of high-intense vortex (and Gaussian) pulsed beam propagation in Kerr media an... more 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.
Nonlinear dynamics of high-intensity femtosecond singular pulses in a Kerr medium with group velo... more Nonlinear dynamics of high-intensity femtosecond singular pulses in a Kerr medium with group velocity dispersion (GVD) is analysed using variational and numerical approaches. We study underlying physical processes governing propagation of vortices: diffraction, Kerr self-focusing, defocusing due to photoinduced plasma, and normal/anomalous GVD. Multifoci behaviour of vortices appearing in the medium are revealed. It is shown that the refocusing period depends on both the magnitude and sign of the GVD. The early stages of vortex beam filamentation are described.
In this work, four-wave difference-frequency generation in centrosymmetric media doped with three... more In this work, four-wave difference-frequency generation in centrosymmetric media doped with three-level quantum systems is investigated theoretically. Terahertz radiation generation in the coherent regime of interaction, where the durations of optical pulses are shorter than the relaxation time of coherences induced in two-and one-photon resonant transitions, is analyzed. It is shown that the coherent regime of four-wave frequency mixing enhances the efficiency of radiation generation in the terahertz frequency range. Quantum confined systems (e.g., atoms and molecules in nanoparticles) should be considered as possible media for practical implementation of the method.
We consider the propagation of terahertz (THz) pulses resonant with the lowest rotational levels ... more We consider the propagation of terahertz (THz) pulses resonant with the lowest rotational levels in ammonia vapors at room temperature. We demonstrate a quasisimultonic regime of propagation for two-color THz pulses (their lossless simultaneous propagation with equal group velocities and stable envelopes at finite distances, like coupled solitons). The quasisimultons are formed by two pulses synchronized in time, the first one being intense and two humped with an area multiple of 4π , while the another one is weaker, one humped, and with an area much less than π. Two-and one-humped pulses have equal width and copropagate in ammonia vapor at the same group velocity. Moreover, the larger the dip of the two-hump pulse is, the weaker may be the one-humped pulse. The stability of this coupled state is provided by the fact that the two-humped pulse makes the medium transparent for the one-humped pulse. In its turn, the latter prevents the breakup of the former into separate pulses. It is established as well that a multihumped pulse with an odd or even number of humps and a hyperbolic secant pulse can behave like a simulton. In this case, the area of multihumped pulse equals to 2nπ , where n is the number of humps in the powerful pulse structure.
We predict and numerically study supercontinuum generation extending over almost two octaves in p... more We predict and numerically study supercontinuum generation extending over almost two octaves in planar rib waveguides, with anomalous dispersion at the input wavelength provided by the waveguide contribution. Such planar nonlinear waveguides generating broadband coherent radiation can be intergrated with other components to constitute a building block in intergrated optical circuits.
The spatiotemporal dynamics of a light pulse injected into a dense, resonant medium under near-di... more The spatiotemporal dynamics of a light pulse injected into a dense, resonant medium under near-dipole-dipole interaction conditions is considered. Two regimes for soliton formation are investigated numerically and analytically. The first one occurs if the pulses are much shorter than both relaxation times. In the second, the pulse duration falls between those of the relaxation times and may be regarded as an incoherent one. In the latter case there are conditions in which the dephasing process is suppressed by dipole-dipole interatomic interaction. Not only are one-soliton solutions found but also a powerful pulse splitting into separate solitons is revealed. The regions in which solitons are found have been estimated. The possibility of finding incoherent solitons has been analyzed, with group-velocity dispersion and diffraction of tilted pulses, which are shown to make soliton formation easier, taken into account.
We study the two-pulse photon echo generation process in thin polymer films doped with organic dy... more We study the two-pulse photon echo generation process in thin polymer films doped with organic dye, when the angle between wave vectors of the excitation pulses is varied. The temporal structure as well as the spectral features of the echo-response are analyzed. The evolution from the gradual blue shift of the echo-signal frequency to the red switch of it is predicted.
The peculiarities of the photon echo signal excitation by two non-collinear pulses in optically d... more The peculiarities of the photon echo signal excitation by two non-collinear pulses in optically dense media are investigated theoretically and numerically. Non-linear evolution of both echo response and exciting pulses is taken into account. Red frequency shift of the primary photon echo signal is predicted.
... Khasanov*, TV Smirnova, OM Fedotova Institute of Solid State and Semiconductors Physics, 17 B... more ... Khasanov*, TV Smirnova, OM Fedotova Institute of Solid State and Semiconductors Physics, 17 Bmvki str., Minsk 220 072, Belarus Abstract The accumulated photon echo (APE) excitation process by N pulse pairs ... Fax: (172) 324694; email: [email protected] ...
... O. Kh. Khasanov, TV Smirnova, and OM Fedotova Institute of Solid-State and Semiconductor Phys... more ... O. Kh. Khasanov, TV Smirnova, and OM Fedotova Institute of Solid-State and Semiconductor Physics, Belarussian Academy of Sciences, ul. Brovki 17, Minsk, 220072 Belarus e-mail: ifttpanb%[email protected] Received July 23, 1996 t3 t3' t2 t1' t4 t4' Tc T ττ p t2 ' ...
Long-lived stimulated photon echo (LSPE) excitation by the sequence ofN pulse pairs in optically ... more Long-lived stimulated photon echo (LSPE) excitation by the sequence ofN pulse pairs in optically thick LaF3:Pr 3+ crystals is investigated numerically. Hyperfine structure of the ground and excited states of medium atoms is taken into account. Stable LSPE amplification along the total sample length is realized in the case when the total initial arca of the pulse sequence is larger than the threshold value r~. Cumulative effect depends on the threshold conditions and the crystal length. At measuring medium spectroscopic parameters the large evaluation errors can be introduced due to neglect of light propagation effects.
We search for efficient schemes of second and terahertz harmonic generation in nanocomposites con... more 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.
We consider the propagation of terahertz (THz) pulses resonant with the lowest rotational levels ... more We consider the propagation of terahertz (THz) pulses resonant with the lowest rotational levels in ammonia vapors at room temperature. We demonstrate a quasisimultonic regime of propagation for two-color THz pulses (their lossless simultaneous propagation with equal group velocities and stable envelopes at finite distances, like coupled solitons). The quasisimultons are formed by two pulses synchronized in time, the first one being intense and two humped with an area multiple of 4π , while the another one is weaker, one humped, and with an area much less than π . Two-and one-humped pulses have equal width and copropagate in ammonia vapor at the same group velocity. Moreover, the larger the dip of the two-hump pulse is, the weaker may be the one-humped pulse. The stability of this coupled state is provided by the fact that the two-humped pulse makes the medium transparent for the one-humped pulse. In its turn, the latter prevents the breakup of the former into separate pulses. It is established as well that a multihumped pulse with an odd or even number of humps and a hyperbolic secant pulse can behave like a simulton. In this case, the area of multihumped pulse equals to 2nπ , where n is the number of humps in the powerful pulse structure.
The structure of software for 3D-simulating processes of echo-responses generation in optically d... more The structure of software for 3D-simulating processes of echo-responses generation in optically dense medium is investigated. Complete analysis of the mathematical model realizing various ways of photon echo generation process in extended samples is presented. The contribution of irreversible relaxation during the whole excitation time and propagation effects caused by a nonlinear medium influence on the exciting pulses and echoresponses are taken into account.
The effect of phase-conjugate feedback on the semiconductor laser dynamics is considered theoreti... more 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.
Dynamics of powerful femtosecond singular-phase pulsed beams in a dielectric medium under the ion... more 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.
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Papers by Olga Fedotova