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Abstract: 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. [Copyright &y& Elsevier]

The temperature effects on the evolution and self-deflection of bright spatial optical solitons in photovoltaic photorefractive media were investigated by taking into account diffusion effects. The numerical results show that the evolution of the bright solitary beam depends strongly on the crystal temperature. It is also found that the bending distance of the bright solitary beam centre increases and reaches its maximum value at a characteristic temperature, and then decreases as temperature rises and approaches zero at low and high temperatures. Both the maximum value and characteristic temperature increase with the input power density. The self-deflection of bright solitary beam is further studied by a perturbation technique, and the results are found to be in good agreement with that obtained by the numerical method. The diffusion process and the dark irradiance dominate the temperature dependence of bending distance in most values of temperature besides at the characteristic temperature and in the higher temperature regime. The diffusion process will mainly dominate the temperature dependence at the characteristic temperature and the dark irradiance will dominate in the higher temperature range. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We provide a comprehensive numerical investigation on the dynamical evolutions, stabilities, and self-deflections of both solitons in a separate dark–dark, bright–dark or bright–bright soliton pair supported by a series photorefractive crystal circuit. The effects of parametric coupling between the two solitons on the evolutions, stabilities and self-deflections of the two soliton are investigated. Results show that whether an optical beam can evolve into a stable solitary state in a crystal depends not only on the initial conditions of that optical beam, but also on the initial conditions of the other optical beam in the other crystal. Changing the input intensity of a dark soliton can affect the self-deflection of other solitons. Some potential applications of the controlled behavior through the dark soliton in the bright–dark soliton pair are discussed. [Copyright &y& Elsevier]

The self-deflection of a solitary wave arising from diffusion effects in a biased photovoltaic photorefractive crystal has been systematically investigated by employing numerical techniques. Adjusting both strength and polarity of the biased field can change the bending angle of the screening-photovoltaic (SP) soliton, and it is more effective by adjusting the polarity than by adjusting the strength. The stronger the input intensity is, the larger the bending angle is for a dark SP soliton, whereas the bending angle tends to decrease for very weak input intensity as well as for a very strong one, and has a larger value between these two regimes for a bright SP soliton. The dark SP soliton deflects left, whereas the bright one deflects right. The self-bending process of a SP soliton still occurs in a lossy crystal. If the input optical beam is a Gauss beam, whether it can evolve into a stable SP bright soliton or not in the crystal, it will bend with distance. [ABSTRACT FROM AUTHOR]

Two-dimensional holographic photovoltaic bright spatial solitons are observed in a Cu:K0.25Na0.75Sr1.5Ba0.5Nb5O15 crystal in which two coherent laser beams, a signal beam, as well as a strong and uniform pump beam at 532 nm are coupled to each other via two-wave mixing. Such solitons originate from the self-trapping of the signal beam due to both photovoltaic effects and holographic focusing effects. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents calculations for an idea in photorefractive spatial solitons, namely, a dissipative holographic soliton and a two-photon-Hamiltonian spatial soliton in one dimension form in an unbiased series photorefractive crystal circuit consisting of a single-photon photorefractive crystals and a two-photon one of which at least one must be photovoltaic. The two solitons are known collectively as a separate Holographic–Hamiltonian spatial soliton pair and there are two types: dark–dark and bright–dark if only one crystal of circuit is photovoltaic. The results show that the two-photon-Hamiltonian soliton in a soliton pair can affect the holographic one by light-induced current and the holographic soliton cannot affect the two-photon-Hamiltonian one. [Copyright &y& Elsevier]

The holographic focusing effects of light in a carbazole photorefractive film at 632.8 nm wavelength were observed without applying a bias field, owing to the two-beam coupling process in the material. The material was prepared from the mixture of 3-formyl-N-vinylcarbazole (99 wt%) and 2,4,7-trinitro-9-fluorenone (1 wt%). [ABSTRACT FROM AUTHOR]

Abstract: To study the grey spatial soliton families in biased two-photon photovoltaic photorefractive crystal, the dynamical evolution equation and the numerical solution of the grey spatial soliton families were established. The numerical results show that the incoherently coupled screening-photovoltaic grey soliton families can be established provided the multiple incident beams have the same polarization, wavelength, and are mutually incoherent. The screening-photovoltaic grey soliton families can be considered as the united form of screening grey soliton families and open- or closed-circuit photovoltaic grey soliton families due to two-photon photorefractive effect. [Copyright &y& Elsevier]

Abstract: We investigate the temporal behavior of low-amplitude dark spatial solitons in biased centrosymmetric crystals with two-photon photorefractive effects. The expressions of time-dependent space-charge field and dynamical evolution equation are derived. The temporal behaviors of the intensity profiles and the intensity full width at half maximum (FWHM) of dark solitons are investigated by numerical method. The results indicate that a broad soliton is generated at the beginning, and as time evolves, the intensity width of solitons decrease monotonously to a minimum value toward steady state. Within the same propagation time, the higher the ratio of soliton peak intensity to the dark irradiation intensity is, the shorter the FWHM of dark solitons is. [Copyright &y& Elsevier]

Abstract: The dielectric properties of near-stoichiometric LiNbO3:Fe single crystal have been investigated by using a terahertz time domain spectroscopy (THz–TDS) in a frequency range of 0.7–1.6THz at room temperature. When coupled with an applied external optical field, an obvious photorefractive effect was observed, resulting in the modulation of the complex dielectric constant for near-SLN:Fe. The variation of refractive index |Δn| has a linear relationship on scale with the applied light intensity accompanied with a steplike decrease. These findings were attributed to the internal space charge field of photorefraction and the light-induced domain reversal in the crystal. [Copyright &y& Elsevier]

Abstract: Dark (bright) steady-state spatial solitons are predicted in one dimension for a series circuit consisting of two two-photon photorefractive crystals of which at least one must be photovoltaic. Each crystal can support a spatial soliton. The two solitons are known collectively as separate spatial soliton pairs with three types: dark–dark, bright–dark and bright–bright. In the limit in which the optical wave has a spatial extent much less than the width of the crystal, the dark soliton can affect the other soliton by light-induced current, but the bright soliton cannot affect the other soliton in the soliton pair. [Copyright &y& Elsevier]