Steady-state Spatial Solitons Research Articles

Separate spatial soliton pairs in an unbiased series two-photon photorefractive crystal circuit

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.

Temporal behavior of dark spatial solitons in closed-circuit photovoltaic media

We show that the time-dependent nonlinear wave equation in closed-circuit photovoltaic media can exhibit quasi-steady-state and steady-state spatial solitons. We demonstrate that the formation time of open-circuit quasi-steady-state and open-circuit steady-state dark solitons decreases with an increase in the intensity ratio of the soliton, which is the ratio between the soliton peak intensity and the dark irradiance. We find that for the time-dependent nonlinear wave equation that exhibits only an open-circuit steady-state dark soliton, changing the electric current density J 0 does not generate quasi-steady-state dark solitons and affects the formation time of steady-state dark solitons and that for the time-dependent nonlinear wave equation that exhibits an open-circuit quasi-steady-state dark soliton, changing J 0 gives rise to three different time evolution regimes of the full width half maximum of the soliton’s intensity. The first regime shows that the formation time of steady-state dark solitons increases with J 0 whereas the formation time of quasi-steady-state dark solitons is independent of J 0 . The second regime shows that the formation time of steady-state dark solitons decreases with an increases in J 0 and the formation time of quasi-steady-state dark solitons increases with J 0 . The third regime shows that changing J 0 enables only steady-state dark solitons in the time-dependent nonlinear wave equation, of which the formation time increases with J 0 .

Separate spatial soliton pairs and solitons interaction in an unbiased series photorefractive crystal circuit

Abstract Dark (bright) steady-state spatial solitons are predicted in one dimension for a series circuit consisting of two photorefractive crystals of which at least one must be photovoltaic. Each crystal can support a spatial soliton. The two solitons are known collectively as a separate spatial soliton pair with three types: bright–bright, bright–dark and dark–dark. In the limit in which the spatial extent of the optical wave is much less than the width of the crystal, the dark soliton can affect the other soliton whereas the bright soliton cannot affect the other soliton in the soliton pair.

Steady-state spatial solitons in biased photovoltaic-photorefractive crystals for short circuits

A theory on spatial solitons in photovoltaic (PV)-photorefractive (PR) crystals for short circuits is developed that gives rise to spatial solitons due to both a bulk PV effect and spatial nonuniform screening of the external field. When the PV effect is neglected these solitons are screening solitons. When the external field is absent these solitons are PV solitons in short and open circuits and it is predicted that grey solitons exist in PV-PR crystals for short circuits. We also show theoretically that PV nonlinearity can be switched from self-defocusing to self-focusing (or vice versa) by adding the external field.

One-dimensional steady-state spatial solitons in photovoltaic photorefractive materials with an external applied field

A theory on spatial solitons in closed-circuit photorefractive-photovoltaic media is developed that gives rise to spatial solitons due to both the bulk photovoltaic effect and the spatially nonuniform screening of the external bias field. In case the photovoltaic effect can be neglected, these solitons are screening solitons. In case the external bias field is absent, these solitons are photovoltaic solitons in the closed-circuit case. We also show theoretically that the photovoltaic nonlinearity can be switched from self-defocusing to self-focusing by adding the external electric field. Under a strong bias condition, the photovoltaic nonlinearity can be switched from self-defocusing to self-focusing by changing the polarity of the external electric field or by rotating the polarization of the light.

Profile of photorefractive one-dimensional bright spatial solitons

Analytic solutions for the profile of one-dimensional bright photorefractive steady-state spatial solitons generated as a result of screening of drift or photogalvanic currents are found by means of a power series development. The solutions are valid over all ranges of intensities. We also give simple analytic expressions that describe the soliton full width at half-maximum as a function of all important experimental parameters.

Effects of optical activity on photorefractive spatial solitons in a biased Bi_12TiO_20 crystal

It is shown that the propagation of steady-state spatial solitons in a bismuth titanium oxide (Bi12TiO20) photorefractive crystal is strongly affected by the presence of concomitant natural optical activity. We assume that the Bi12TiO20 crystal is (110) cut and that the external bias field is along the [001¯] axis. Such orientation introduces self-focusing in one polarization of an optical wave front, whereas it has no effect whatsoever on the component orthogonal to it. Under these conditions, the equations that describe the coupled evolution of the two polarizations of an optical planar beam are derived. Our numerical study of the interaction dynamics shows that, even though the optical beam experiences periodic diffraction in one of the polarization components, it can still recover significantly at particular distances within the crystal. Moreover, it is initially capable of maintaining its solitonlike form over a certain distance of propagation. Relevant examples are provided.