Separate Soliton Pair Research Articles

Coupling of separate solitons in a series circuit of two photon photorefractive crystals exhibiting simultaneous quadratic and linear nonlinearities

Separately coupled optical spatial solitons are shown to exist in a biased series two-photon photorefractive(TPPR) crystal circuit consisting of two TPPR crystals which have the quadratic and linear electro-optic(EO) effect present simultaneously. The space charge field in each photorefractive(PR) crystal in the circuit has been derived. We find that the space charge field in each crystal is coupled with the space charge field in the other crystal. We consider the cases of separately coupled bright, dark and grey solitons and obtain the numerical solutions for the spatial solitons’ profile. The coupling effect due to the soliton peak intensity in each crystal and the gating beam intensity is studied in detail. The light induced current causes a change in the spatial profile of the dark or grey soliton in one of the crystal which results in a change in the spatial profile and propagation of the soliton in the other crystal. We also find that the bright soliton intensity in one crystal does not affect the soliton in the other crystal. A change in the gating beam intensity in one crystal influences the soliton in the other crystal and this is true for all the three cases of dark, grey and bright separate soliton pairs.

Separate holographic-Hamiltonian screening soliton pairs in a biased series photorefractive crystal circuit

Separate holographic-Hamiltonian screening soliton pairs are predicted in a biased series photorefractive crystal circuit consisting of two photorefractive crystals connected electronically by electrode leads in a chain with a voltage source. The existence of four types of the separate soliton pairs:dark-dark, bright-dark, dark-bright and bright-bright, in such a circuit is proved. Under the limit that the spatial extent of the optical wave is much less than the width of the crystal, the Hamiltonian dark soliton can affect the other soliton by the light-induced current whereas the Hamiltonian bright soliton and holographic soliton cannot affect the other soliton in the soliton pair.

Separate Holographic-Hamiltonian screening soliton pairs in a biased series photorefractive crystal circuit

Separate Holographic-Hamiltonian screening soliton pairs are predicted in a biased series photorefractive crystal circuit consisting of two photorefractive crystals connected electronically by electrode leads in a chain with a voltage source. The existence of four types of the separate soliton pairs: dark–dark, bright–dark, dark–bright and bright–bright in such a circuit is proved. Under the limit in which the spatial extent of the optical wave is much less than the width of the crystal, the Hamiltonian dark soliton can affect the other soliton by the light-induced current whereas the Hamiltonian bright soliton and holographic soliton cannot affect the other soliton in the soliton pair.

Separate spatial soliton pairs in a biased series centrosymmetric photorefractive crystal circuit

It is shown theoretically that three types of separate soliton pairs: bright–bright, bright–dark, and dark–dark, can be established in a biased series circuit consisting of two centrosymmetric photorefractive crystals and the two solitons in a separate soliton pair can affect each other by the light-induced current. The effects of the intensities of soliton beams and background lights on the normalized profiles of solitons are discussed.

Temperature effects of dark solitons on the self-deflection of bright solitons in a separate bright-dark soliton pair

Based on the theory of one-dimensional separate soliton pairs formed in a serial photorefractive crystal circuit, we investigated the temperature effects of the dark soliton on the self-deflection of the bright soliton in a bright-dark soliton pair. The numerical results obtained by solving the nonlinear propagation equation showed that the bright soliton moves on a parabolic trajectory in the crystal and its spatial shift changed with the temperature of the dark soliton. The higher the temperature of the dark soliton was, the smaller the spatial shift of the bright soliton was. The self-bending process was further studied by the perturbation technique, and the results were found to be in good agreement with that obtained by the numerical method.

Effects of dark soliton crystal temperature on the self-deflection of bright soliton in a biased serial photovoltaic photorefractive crystal circuit

Based on the theory of one-dimensional separate soliton pairs formed in a serial photovoltaic photorefractive crystal circuit, the effects of the dark soliton crystal temperature on the self-deflection of the bright one in a bright–dark soliton pair are investigated. The numerical results indicate that the spatial shift of the bright soliton can experience obvious increase in their self-deflection with the increase of the temperature of the dark soliton. The self-bending process is further studied using perturbation techniques and the results are found to be good agreement with that obtained by numerical method.

Effects of dark soliton on self-deflection of bright soliton in a separate bright-dark soliton pair

Based on the theory of one-dimensional separate soliton pairs formed in a serial photorefractive crystal circuit, the effects of the dark soliton on the self-deflection of the bright one in one separate bright-dark soliton pair are investigated by taking the diffusion term into account. The numerical results obtained by solving the nonlinear propagation equation show that the bright soliton moves on a parabolic trajectory in the crystal and its spatial shift changes with the input intensity of the dark soliton. These effects are further studied using perturbation analysis and the characteristics of the spatial shift of the bright soliton varying with the input maximum intensity of the dark soltion are analysed. The position of the bright soliton at the output surface of the crystal can be determined accurately according to the formula obtained from perturbation method.

Effects of dark soliton on self-deflection of bright soliton in a separate bright-dark soliton pair

Abstract Based on the theory of one-dimensional separate soliton pairs formed in a serial photorefractive crystal circuit, the effects of the dark soliton on the self-deflection of the bright one in one separate bright-dark soliton pair are investigated by taking the diffusion term into account. The numerical results obtained by solving the nonlinear propagation equation show that the bright soliton moves on a parabolic trajectory in the crystal and its spatial shift changes with the input intensity of the dark soliton. These effects are further studied using perturbation analysis and the characteristics of the spatial shift of the bright soliton varying with the input maximum intensity of the dark soltion are analysed. The position of the bright soliton at the output surface of the crystal can be determined accurately according to the formula obtained from perturbation method.

Femtosecond dynamics of mixed gap states in conducting polymers

We numerically apply a femtosecond electric pump pulse to a bond-disordered polymer chain in the Su-Schrieffer-Heeger model and observe the formation of localized excitations, particularly bound and separate soliton pairs with a partial occupation of the gap states. Mixed gap states are also found in the mean field dynamics of an electron hole-pair. They are significant optical excitations in conjugated polymers. The ground state of a chain with mixed gap states shows a discontinuous phase transition from bound to separate soliton pairs. We investigate their dynamics under the influence of a dc pump pulse as well as from initial electron hole-pair excitation using ‘mean field’ instead of the often applied ‘adiabatic’ dynamics.

Dynamics of a bond-disordered Peierls chain and mixed gap states

We numerically apply a femtosecond electric pump pulse to a bond-disordered Su-Schrieffer-Heeger model and observe the formation of excitations like bound and separate soliton pairs as well as neutral localized breathers. Bound soliton pairs though overall charge neutral show an electric dipole moment oscillating with the transition frequency between the partially occupied gap states. Furthermore, the dipole moment amplitude pulsates while the solitons are interacting with the localized breathers. We investigate the ground state and dynamics of the bound soliton pairs as mixed gap states. In their ground state a discontinuous phase transition from bound to separate soliton pairs is found. The dynamics of these states is very similar to the dynamics under the pump-pulse excitation. We discuss their ground state and the dynamics in terms of the soliton-pair solution of the continuum model.