Solange Cavalcanti - Academia.edu (original) (raw)

Papers by Solange Cavalcanti

Research paper thumbnail of Cloning, Breakup, and Soliton Interactions∗

soliton propagation through doped optical fibers:

Research paper thumbnail of Quantum interference of nondiffracting beams

We report a quantum interference of nondiffracting beams by using photon pairs generated by spont... more We report a quantum interference of nondiffracting beams by using photon pairs generated by spontaneous parametric down-conversion. The photon pairs transmitted by two double annular aperture produce fourth-order interference pattern along the transverse plane of detection as well as along the propagation distance. The latter presents a typical behaviour of the so-called Talbot effect . Introduction During the last few years, the properties of nondiffracting beams [1], also known as Bessel beams, have received attention by various authors. Recently, the superluminal behavior of these beams has been under investigation from a theoretical [2] and an experimental [3] point of view. An interesting self-imaging effect phenomenon, resulting from the superposition of two Bessel beams propagating in free space, has been predicted and experimentally demonstrated at a classical level [4]. On the other hand, the correlated photon pairs generated by spontaneous parametric down-conversion produc...

Research paper thumbnail of Light propagation and Anderson localization in superlattices containing metamaterials: effects of correlated disorder

We have investigated the effects of disorder correlations on light propagation and Anderson local... more We have investigated the effects of disorder correlations on light propagation and Anderson localization in one-dimensional dispersive metamaterials. We consider and compare the cases where disorder is uncorrelated to situations where it is totally correlated and anti-correlated. The photonic gaps of the corresponding periodic structure are not completely destroyed by the presence of disorder, which leads to minima in the localization length. In the vicinities of a gap, the behavior of the localization length depends crucially on the physical origin of the gap (Bragg or non-Bragg gaps). Within a Bragg gap, the localization length increases as the degree of disorder increases, an anomalous behavior that only occurs for the uncorrelated and completely correlated cases. In these cases, minima of the localization length at the positions of Bragg gaps are shifted by increasing disorder, which does not occur for the anti-correlated case, where the positions of the minima remain unaltered. Minima in the localization length corresponding to non-Bragg gaps are not shifted by increasing disorder, albeit the widths of these minima are changed. We have found that the asymptotic behavior for the localization length ξ ∝ λ 6 for disordered metamaterials is not affected by correlations. Finally, we have investigated the role of absorption on the delocalized Brewster modes and argue that it could be mitigated in the light of the state-of-the-art of metamaterials research.

Research paper thumbnail of Bragg-induced oscillations in non-PT photonic lattices

arXiv: Optics, 2017

When a monochromatic beam of light propagates through a periodic structure with the incident angl... more When a monochromatic beam of light propagates through a periodic structure with the incident angle satisfying the Bragg condition, its Fourier spatial spectra oscillates between the resonant modes situated on the edges of the Brillouin zones of the lattice with a nontrivial dynamics. We wish to study here these Bragg-induced oscillations in a specific non-PT periodic structure, that is, a periodic medium not invariant under the combined action of parity and time reversal symmetries. We compare our analytic results based on the expansion of the optical field in Bragg-resonant plane waves with direct numerical integration of the paraxial wave equation using a wide Gaussian beam as initial condition without assuming the shallow potential approximation. In particular, we wish to investigate under what conditions a mode trapping phenomenon can still be observed and to verify closely how the energy exchange between the spectral modes takes place during propagation in this more general cla...

Research paper thumbnail of Stationary states in a pair of tunnel-coupled two-dimensional condensates with the scattering lengths of opposite sign

arXiv: Other Condensed Matter, 2004

We study, analytically and numerically, the stationary states in the system of two linearly coupl... more We study, analytically and numerically, the stationary states in the system of two linearly coupled nonlinear Schr{\"o}dinger equations in two spatial dimensions, with the nonlinear interaction coefficients of opposite signs. This system is the two-dimensional analog of the coupled-mode equations for a condensate in the double-well trap [\textit{Physical Review A} \textbf{69}, 033609 (2004)]. In contrast to the one-dimensional case, where the bifurcation from zero leads to stable bright solitons, in two spatial dimensions this bifurcation results in the appearance of unstable soliton solutions (the Townes-type solitons). With the use of a parabolic potential the ground state of the system is stabilized. It corresponds to strongly coupled condensates and is stable with respect to collapse. This is in sharp contrast to the one-dimensional case, where the ground state corresponds to weakly coupled condensates and is unstable. Moreover, the total number of atoms of the stable groun...

Research paper thumbnail of Dynamics of Femtosecond Pulses in the Region of Zero Secoind Order Dispersion of Single Mode Optical Fibers

The evolution of femtosecond optical pulses in the region of minimum group velocity disper- sion ... more The evolution of femtosecond optical pulses in the region of minimum group velocity disper- sion of single mode optical fibers is analyzed numerically, by means of an extended nonlinear Schrodinger equation. Besides spectral fragmentation with formation of femtosecond optical solitons and dispersive waves, the results revealed new features of the pulse evolution owing to the intrapulse stimulated Raman scattering effect. tween theoreti~al(~l~I and e~~erimental(~~~ I results re- lated to thr pulse evolution and frequency shift of the solitary waves with pulse amplitude was obtained. The discrepsncies were mainly due to the fact that in the e~~eriment(~~~), femtosecond input pulses were uti- lized, while in the the~r~(~l~), a few picosecond input pulsewidths were assumed. The predictions of the non- linear Schro'linger equation are accurate for picosecond pulses but rieed to be modified for femtosecond input pulses, as severa1 higher-order nonlinear effects become important for su...

Research paper thumbnail of Bragg-induced power oscillations in PT -symmetric periodic photonic structures

Physical Review A

We study Bragg-induced power oscillations in Fourier space between a pair of optical resonant tra... more We study Bragg-induced power oscillations in Fourier space between a pair of optical resonant transverse modes propagating through a periodic PT symmetric lattice, represented by a refractive index that includes gain and loss in a balanced way. Our results imply that the PT-symmetric system shows exceptionally rich phenomena absent in its Hermitian counterpart. It is demonstrated that the resonant modes exhibit unique characteristics such as Bragg power oscillations controlled via the PT symmetry, severe asymmetry in mode dynamics, and trapped enhanced transmission. We have also performed numerical simulations in (1+1) and (2+1) dimensions of propagating Gaussian beams to compare with analytical calculations developed under a two-waves model.

Research paper thumbnail of Zero- ϕ eff non-Bragg gap solitons in 1D Kerr polaritonic/metamaterial heterostructures

Physica E: Low-dimensional Systems and Nanostructures

Abstract A theoretical study of one-dimensional heterostructures composed of alternate layers of ... more Abstract A theoretical study of one-dimensional heterostructures composed of alternate layers of a Kerr polaritonic material and a linear dispersive metamaterial is performed. For frequency values at the edges of the non-Bragg zero- ϕ eff gap of the heterostructure in the linear regime, a switching from very low to high transmission states is obtained and localized gap solitons of various orders are found, depending on the particular value of the incident power. Soliton solutions are shown to be robust with respect to absorption effects and a study is presented for gap soliton phases at the top and bottom of the zero- ϕ eff gap in the case of defocusing and focusing nonlinearities.

Research paper thumbnail of Soliton-induced transparency in disordered Kerr-metamaterial heterostructures

Journal of the Optical Society of America B

The optical transmission properties of light in one-dimensional disordered nonlinear layered syst... more The optical transmission properties of light in one-dimensional disordered nonlinear layered systems with metamaterial inclusions are theoretically studied. Layer widths of both nonlinear and metamaterial slabs are considered as random variables without any correlation between them. A thorough investigation of the influence of disorder in the vicinities of a Bragg gap, a zero-n gap, and a bulk-like longitudinal plasmon–polariton gap is performed. Disorder effects result in a considerable broadness of the transmission peaks as compared with periodic nondisordered structures. It is shown that the Bragg-gap soliton reveals itself as the most robust against disorder.

Research paper thumbnail of Localized modes inχ(2)media with non-PT-symmetric complex localized potentials

Physical Review A

We study the existence and the stability of solitons in quadratic nonlinear media with spatially ... more We study the existence and the stability of solitons in quadratic nonlinear media with spatially localized non-PT-symmetric tunable modulation of the linear refractive index. The properties of nonlinear modes bifurcating from a linear limit of a small fundamental harmonic field are investigated. The modes bifurcating from the linear mode of the second harmonic may exist even above the real phase breaking threshold. The stability intervals for different values of the propagation constant and gain-loss gradient are obtained. Examples of dynamics and excitations of solitons obtained by numerical simulations are also given.

Research paper thumbnail of Soliton interaction control in coherently excited three-level system embedded in a nonlinear waveguide

We investigate the properties of the interaction between a pair of solitons that are originated f... more We investigate the properties of the interaction between a pair of solitons that are originated from the breakup dynamics of a high order soliton propagating through a cylindrical waveguide in the presence of three-level resonances associated with a dopant. We find that the nature of this interaction may be controlled by varying the initial intensity ratio and overlap between pump and signal from which the pair was originated.

Research paper thumbnail of An analogy between state transfer in spin chains and spontaneous emission

In this work we highlight an analogy between a spontaneous population decay via an interaction of... more In this work we highlight an analogy between a spontaneous population decay via an interaction of emitters with bosonic reservoirs and a qubit transfer in spin chains. This analogy allows to implement spin chains for reproducing the complicated emitter dynamics (i.e. oscillatory decay and ‘freezing’ of decay) expected to appear in structured reservoirs, such as photonic crystals with band‐gaps. Also, this analogy opens new ways to engineer spin chains for an efficient state transfer robust with respect to perturbations of spin chain parameters.

Research paper thumbnail of Scattering of partially coherent radiation by non-Hermitian localized structures having parity-time symmetry

Physical Review A

A theoretical model based on two point scatterers is suggested to investigate for the first time ... more A theoretical model based on two point scatterers is suggested to investigate for the first time scattering of partially coherent radiation by a non-Hermitian localized structure, invariant under the simultaneous symmetry operations of parity inversion and time reversal. Within the first-order Born approximation, and the formalism of classical coherence theory, the spectral density of the scattered field in the far-zone is obtained analytically. We find that the unidirectional character of the scattered radiation, which is one of the principal effects present in non-Hermitian structures, may be suppressed due to the coherence properties of the radiation without changing the geometry of the structure. Asymmetric spectral changes of the scattered radiation due to the non-Hermitian character of the material is also observed. I.

Research paper thumbnail of Asymmetries in the tunneling probability of Bose-Einstein condensate in an accelerating optical lattice

We derive a two-band finite-dimensional model for description of the condensate tunneling in an a... more We derive a two-band finite-dimensional model for description of the condensate tunneling in an accelerating optical lattice, taking into account the fine Bloch band structure. The model reveals a very strong dependence of the final band populations on the initial populations and phases. Most importantly, additionally to the known asymmetric dependence on the nonlinearity, there is also a notable asymmetry in the sensitivity of the tunneling probability to the nonliearity-induced initial population of the Bloch band to which the tunneling takes place. This fact can explain the experimentally observed unexpected independence of the upper-to-lower tunneling probablity on the nonlinearity. Finally, we compare the predictions of the two-band model with that of the well-known nonlinear Landau-Zener model and find disagreement when the two bands are initially populated. The disagreement can be qualitative and reveals itself even for a negligible nonlinearity. However, the two models agree...

Research paper thumbnail of Modulational instability in semiconductor-doped glass fibers with saturable nonlinearity

Optics Letters, 1993

Modulational instability in doped glass fibers is analyzed theoretically in a steady-state regime... more Modulational instability in doped glass fibers is analyzed theoretically in a steady-state regime, taking into account a saturable nonlinearity. The results have shown that the critical modulation frequency and modulation gain increase with input power, reaching a maximum value at the saturation power. This leads to a unique value of the critical modulation frequency for two different input powers so that two solutions will experience a maximum gain at the same frequency. Modulational instability in silica-based glass fibers has already been studied both theoretically and experimentally by many, as reviewed in Ref. 1. The mechanism permits the generation of ultrashort pulse trains with repetition rates in the range 300 GHz to 8 THz. 2-4 This mechanism is also one of the

Research paper thumbnail of <title>A 2D honeycomb photonic crystal under applied magnetic fields</title>

Photonics, Devices, and Systems IV, 2008

Research paper thumbnail of Zener Tunnelling in Periodic Two-Dimensional Photonic Lattices with Three-fold Symmetry

2007 9th International Conference on Transparent Optical Networks, 2007

We study the interband wave tunnelling (Zener transitions) in two-dimensional hexagonal lattices ... more We study the interband wave tunnelling (Zener transitions) in two-dimensional hexagonal lattices with superimposed index gradient and derive simple analytical models capturing the essence of the tunnelling phenomenon. We find that the two-dimensional tunnelling in hexagonal lattices occurs at the high-symmetry points (e.g., the M and lceil points), and it involves either three or six Bloch bands being described by

Research paper thumbnail of <title>A taste of photonics: band structure, null gaps, non-Bragg gaps, and symmetry properties of one-dimensional superlattices</title>

ICONO 2007: Physics of Intense and Superintense Laser Fields; Attosecond Pulses; Quantum and Atomic Optics; and Engineering of Quantum Information, 2007

We have investigated the propagation of plane waves through one-dimensional superlattices compose... more We have investigated the propagation of plane waves through one-dimensional superlattices composed of alternate layers characterized by two di.erent refractive indexes, which may take on positive as well as negative values. For both indices of refraction positive we have found null-gap points for commensurate values of the optical path lengths of each layer at which the superlattice becomes transparent. We

Research paper thumbnail of Rabi oscillation damping of two-level states in quantum dots

Physica E: Low-Dimensional Systems and Nanostructures, 2008

Within a general approach suitable to describe a coherently driven two-level system interacting w... more Within a general approach suitable to describe a coherently driven two-level system interacting with a dephasing reservoir, we have proposed various mechanisms to explain the nature of the damping of Rabi oscillations with increasing driving-pulse area in localized two-level semiconductor systems. We have shown that the non-Markovian character of the reservoir leads to the dependence of the dephasing rate on

Research paper thumbnail of Entanglement induced by noise: Emitters in thermal bandgap reservoirs

Physica E: Low-Dimensional Systems and Nanostructures, 2008

ABSTRACT Emitter-field interactions in a bandgap reservoir at a finite temperature are investigat... more ABSTRACT Emitter-field interactions in a bandgap reservoir at a finite temperature are investigated by means of a time-local Lindblad master equation derived specifically for this purpose. It is demonstrated that the entangled field-emitter state that arises as a result of the interaction does not survive at finite temperatures. On the other hand, the probability to excite such an entangled state by thermal excitation is found to be close to unity.

Research paper thumbnail of Cloning, Breakup, and Soliton Interactions∗

soliton propagation through doped optical fibers:

Research paper thumbnail of Quantum interference of nondiffracting beams

We report a quantum interference of nondiffracting beams by using photon pairs generated by spont... more We report a quantum interference of nondiffracting beams by using photon pairs generated by spontaneous parametric down-conversion. The photon pairs transmitted by two double annular aperture produce fourth-order interference pattern along the transverse plane of detection as well as along the propagation distance. The latter presents a typical behaviour of the so-called Talbot effect . Introduction During the last few years, the properties of nondiffracting beams [1], also known as Bessel beams, have received attention by various authors. Recently, the superluminal behavior of these beams has been under investigation from a theoretical [2] and an experimental [3] point of view. An interesting self-imaging effect phenomenon, resulting from the superposition of two Bessel beams propagating in free space, has been predicted and experimentally demonstrated at a classical level [4]. On the other hand, the correlated photon pairs generated by spontaneous parametric down-conversion produc...

Research paper thumbnail of Light propagation and Anderson localization in superlattices containing metamaterials: effects of correlated disorder

We have investigated the effects of disorder correlations on light propagation and Anderson local... more We have investigated the effects of disorder correlations on light propagation and Anderson localization in one-dimensional dispersive metamaterials. We consider and compare the cases where disorder is uncorrelated to situations where it is totally correlated and anti-correlated. The photonic gaps of the corresponding periodic structure are not completely destroyed by the presence of disorder, which leads to minima in the localization length. In the vicinities of a gap, the behavior of the localization length depends crucially on the physical origin of the gap (Bragg or non-Bragg gaps). Within a Bragg gap, the localization length increases as the degree of disorder increases, an anomalous behavior that only occurs for the uncorrelated and completely correlated cases. In these cases, minima of the localization length at the positions of Bragg gaps are shifted by increasing disorder, which does not occur for the anti-correlated case, where the positions of the minima remain unaltered. Minima in the localization length corresponding to non-Bragg gaps are not shifted by increasing disorder, albeit the widths of these minima are changed. We have found that the asymptotic behavior for the localization length ξ ∝ λ 6 for disordered metamaterials is not affected by correlations. Finally, we have investigated the role of absorption on the delocalized Brewster modes and argue that it could be mitigated in the light of the state-of-the-art of metamaterials research.

Research paper thumbnail of Bragg-induced oscillations in non-PT photonic lattices

arXiv: Optics, 2017

When a monochromatic beam of light propagates through a periodic structure with the incident angl... more When a monochromatic beam of light propagates through a periodic structure with the incident angle satisfying the Bragg condition, its Fourier spatial spectra oscillates between the resonant modes situated on the edges of the Brillouin zones of the lattice with a nontrivial dynamics. We wish to study here these Bragg-induced oscillations in a specific non-PT periodic structure, that is, a periodic medium not invariant under the combined action of parity and time reversal symmetries. We compare our analytic results based on the expansion of the optical field in Bragg-resonant plane waves with direct numerical integration of the paraxial wave equation using a wide Gaussian beam as initial condition without assuming the shallow potential approximation. In particular, we wish to investigate under what conditions a mode trapping phenomenon can still be observed and to verify closely how the energy exchange between the spectral modes takes place during propagation in this more general cla...

Research paper thumbnail of Stationary states in a pair of tunnel-coupled two-dimensional condensates with the scattering lengths of opposite sign

arXiv: Other Condensed Matter, 2004

We study, analytically and numerically, the stationary states in the system of two linearly coupl... more We study, analytically and numerically, the stationary states in the system of two linearly coupled nonlinear Schr{\"o}dinger equations in two spatial dimensions, with the nonlinear interaction coefficients of opposite signs. This system is the two-dimensional analog of the coupled-mode equations for a condensate in the double-well trap [\textit{Physical Review A} \textbf{69}, 033609 (2004)]. In contrast to the one-dimensional case, where the bifurcation from zero leads to stable bright solitons, in two spatial dimensions this bifurcation results in the appearance of unstable soliton solutions (the Townes-type solitons). With the use of a parabolic potential the ground state of the system is stabilized. It corresponds to strongly coupled condensates and is stable with respect to collapse. This is in sharp contrast to the one-dimensional case, where the ground state corresponds to weakly coupled condensates and is unstable. Moreover, the total number of atoms of the stable groun...

Research paper thumbnail of Dynamics of Femtosecond Pulses in the Region of Zero Secoind Order Dispersion of Single Mode Optical Fibers

The evolution of femtosecond optical pulses in the region of minimum group velocity disper- sion ... more The evolution of femtosecond optical pulses in the region of minimum group velocity disper- sion of single mode optical fibers is analyzed numerically, by means of an extended nonlinear Schrodinger equation. Besides spectral fragmentation with formation of femtosecond optical solitons and dispersive waves, the results revealed new features of the pulse evolution owing to the intrapulse stimulated Raman scattering effect. tween theoreti~al(~l~I and e~~erimental(~~~ I results re- lated to thr pulse evolution and frequency shift of the solitary waves with pulse amplitude was obtained. The discrepsncies were mainly due to the fact that in the e~~eriment(~~~), femtosecond input pulses were uti- lized, while in the the~r~(~l~), a few picosecond input pulsewidths were assumed. The predictions of the non- linear Schro'linger equation are accurate for picosecond pulses but rieed to be modified for femtosecond input pulses, as severa1 higher-order nonlinear effects become important for su...

Research paper thumbnail of Bragg-induced power oscillations in PT -symmetric periodic photonic structures

Physical Review A

We study Bragg-induced power oscillations in Fourier space between a pair of optical resonant tra... more We study Bragg-induced power oscillations in Fourier space between a pair of optical resonant transverse modes propagating through a periodic PT symmetric lattice, represented by a refractive index that includes gain and loss in a balanced way. Our results imply that the PT-symmetric system shows exceptionally rich phenomena absent in its Hermitian counterpart. It is demonstrated that the resonant modes exhibit unique characteristics such as Bragg power oscillations controlled via the PT symmetry, severe asymmetry in mode dynamics, and trapped enhanced transmission. We have also performed numerical simulations in (1+1) and (2+1) dimensions of propagating Gaussian beams to compare with analytical calculations developed under a two-waves model.

Research paper thumbnail of Zero- ϕ eff non-Bragg gap solitons in 1D Kerr polaritonic/metamaterial heterostructures

Physica E: Low-dimensional Systems and Nanostructures

Abstract A theoretical study of one-dimensional heterostructures composed of alternate layers of ... more Abstract A theoretical study of one-dimensional heterostructures composed of alternate layers of a Kerr polaritonic material and a linear dispersive metamaterial is performed. For frequency values at the edges of the non-Bragg zero- ϕ eff gap of the heterostructure in the linear regime, a switching from very low to high transmission states is obtained and localized gap solitons of various orders are found, depending on the particular value of the incident power. Soliton solutions are shown to be robust with respect to absorption effects and a study is presented for gap soliton phases at the top and bottom of the zero- ϕ eff gap in the case of defocusing and focusing nonlinearities.

Research paper thumbnail of Soliton-induced transparency in disordered Kerr-metamaterial heterostructures

Journal of the Optical Society of America B

The optical transmission properties of light in one-dimensional disordered nonlinear layered syst... more The optical transmission properties of light in one-dimensional disordered nonlinear layered systems with metamaterial inclusions are theoretically studied. Layer widths of both nonlinear and metamaterial slabs are considered as random variables without any correlation between them. A thorough investigation of the influence of disorder in the vicinities of a Bragg gap, a zero-n gap, and a bulk-like longitudinal plasmon–polariton gap is performed. Disorder effects result in a considerable broadness of the transmission peaks as compared with periodic nondisordered structures. It is shown that the Bragg-gap soliton reveals itself as the most robust against disorder.

Research paper thumbnail of Localized modes inχ(2)media with non-PT-symmetric complex localized potentials

Physical Review A

We study the existence and the stability of solitons in quadratic nonlinear media with spatially ... more We study the existence and the stability of solitons in quadratic nonlinear media with spatially localized non-PT-symmetric tunable modulation of the linear refractive index. The properties of nonlinear modes bifurcating from a linear limit of a small fundamental harmonic field are investigated. The modes bifurcating from the linear mode of the second harmonic may exist even above the real phase breaking threshold. The stability intervals for different values of the propagation constant and gain-loss gradient are obtained. Examples of dynamics and excitations of solitons obtained by numerical simulations are also given.

Research paper thumbnail of Soliton interaction control in coherently excited three-level system embedded in a nonlinear waveguide

We investigate the properties of the interaction between a pair of solitons that are originated f... more We investigate the properties of the interaction between a pair of solitons that are originated from the breakup dynamics of a high order soliton propagating through a cylindrical waveguide in the presence of three-level resonances associated with a dopant. We find that the nature of this interaction may be controlled by varying the initial intensity ratio and overlap between pump and signal from which the pair was originated.

Research paper thumbnail of An analogy between state transfer in spin chains and spontaneous emission

In this work we highlight an analogy between a spontaneous population decay via an interaction of... more In this work we highlight an analogy between a spontaneous population decay via an interaction of emitters with bosonic reservoirs and a qubit transfer in spin chains. This analogy allows to implement spin chains for reproducing the complicated emitter dynamics (i.e. oscillatory decay and ‘freezing’ of decay) expected to appear in structured reservoirs, such as photonic crystals with band‐gaps. Also, this analogy opens new ways to engineer spin chains for an efficient state transfer robust with respect to perturbations of spin chain parameters.

Research paper thumbnail of Scattering of partially coherent radiation by non-Hermitian localized structures having parity-time symmetry

Physical Review A

A theoretical model based on two point scatterers is suggested to investigate for the first time ... more A theoretical model based on two point scatterers is suggested to investigate for the first time scattering of partially coherent radiation by a non-Hermitian localized structure, invariant under the simultaneous symmetry operations of parity inversion and time reversal. Within the first-order Born approximation, and the formalism of classical coherence theory, the spectral density of the scattered field in the far-zone is obtained analytically. We find that the unidirectional character of the scattered radiation, which is one of the principal effects present in non-Hermitian structures, may be suppressed due to the coherence properties of the radiation without changing the geometry of the structure. Asymmetric spectral changes of the scattered radiation due to the non-Hermitian character of the material is also observed. I.

Research paper thumbnail of Asymmetries in the tunneling probability of Bose-Einstein condensate in an accelerating optical lattice

We derive a two-band finite-dimensional model for description of the condensate tunneling in an a... more We derive a two-band finite-dimensional model for description of the condensate tunneling in an accelerating optical lattice, taking into account the fine Bloch band structure. The model reveals a very strong dependence of the final band populations on the initial populations and phases. Most importantly, additionally to the known asymmetric dependence on the nonlinearity, there is also a notable asymmetry in the sensitivity of the tunneling probability to the nonliearity-induced initial population of the Bloch band to which the tunneling takes place. This fact can explain the experimentally observed unexpected independence of the upper-to-lower tunneling probablity on the nonlinearity. Finally, we compare the predictions of the two-band model with that of the well-known nonlinear Landau-Zener model and find disagreement when the two bands are initially populated. The disagreement can be qualitative and reveals itself even for a negligible nonlinearity. However, the two models agree...

Research paper thumbnail of Modulational instability in semiconductor-doped glass fibers with saturable nonlinearity

Optics Letters, 1993

Modulational instability in doped glass fibers is analyzed theoretically in a steady-state regime... more Modulational instability in doped glass fibers is analyzed theoretically in a steady-state regime, taking into account a saturable nonlinearity. The results have shown that the critical modulation frequency and modulation gain increase with input power, reaching a maximum value at the saturation power. This leads to a unique value of the critical modulation frequency for two different input powers so that two solutions will experience a maximum gain at the same frequency. Modulational instability in silica-based glass fibers has already been studied both theoretically and experimentally by many, as reviewed in Ref. 1. The mechanism permits the generation of ultrashort pulse trains with repetition rates in the range 300 GHz to 8 THz. 2-4 This mechanism is also one of the

Research paper thumbnail of <title>A 2D honeycomb photonic crystal under applied magnetic fields</title>

Photonics, Devices, and Systems IV, 2008

Research paper thumbnail of Zener Tunnelling in Periodic Two-Dimensional Photonic Lattices with Three-fold Symmetry

2007 9th International Conference on Transparent Optical Networks, 2007

We study the interband wave tunnelling (Zener transitions) in two-dimensional hexagonal lattices ... more We study the interband wave tunnelling (Zener transitions) in two-dimensional hexagonal lattices with superimposed index gradient and derive simple analytical models capturing the essence of the tunnelling phenomenon. We find that the two-dimensional tunnelling in hexagonal lattices occurs at the high-symmetry points (e.g., the M and lceil points), and it involves either three or six Bloch bands being described by

Research paper thumbnail of <title>A taste of photonics: band structure, null gaps, non-Bragg gaps, and symmetry properties of one-dimensional superlattices</title>

ICONO 2007: Physics of Intense and Superintense Laser Fields; Attosecond Pulses; Quantum and Atomic Optics; and Engineering of Quantum Information, 2007

We have investigated the propagation of plane waves through one-dimensional superlattices compose... more We have investigated the propagation of plane waves through one-dimensional superlattices composed of alternate layers characterized by two di.erent refractive indexes, which may take on positive as well as negative values. For both indices of refraction positive we have found null-gap points for commensurate values of the optical path lengths of each layer at which the superlattice becomes transparent. We

Research paper thumbnail of Rabi oscillation damping of two-level states in quantum dots

Physica E: Low-Dimensional Systems and Nanostructures, 2008

Within a general approach suitable to describe a coherently driven two-level system interacting w... more Within a general approach suitable to describe a coherently driven two-level system interacting with a dephasing reservoir, we have proposed various mechanisms to explain the nature of the damping of Rabi oscillations with increasing driving-pulse area in localized two-level semiconductor systems. We have shown that the non-Markovian character of the reservoir leads to the dependence of the dephasing rate on

Research paper thumbnail of Entanglement induced by noise: Emitters in thermal bandgap reservoirs

Physica E: Low-Dimensional Systems and Nanostructures, 2008

ABSTRACT Emitter-field interactions in a bandgap reservoir at a finite temperature are investigat... more ABSTRACT Emitter-field interactions in a bandgap reservoir at a finite temperature are investigated by means of a time-local Lindblad master equation derived specifically for this purpose. It is demonstrated that the entangled field-emitter state that arises as a result of the interaction does not survive at finite temperatures. On the other hand, the probability to excite such an entangled state by thermal excitation is found to be close to unity.