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1.
Separate holographic screening soliton pairs in a biased series photorefractive crystal circuit
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Holographic dark (bright) screening solitons are predicted
in one dimension for a series circuit consisting of two
photorefractive crystals connected electronically by electrode leads
in a chain with a voltage source. Each crystal can support a
holographic screening soliton. The two solitons are known
collectively as a separate holographic screening soliton pair with
three types: bright--bright, bright--dark and dark--dark. The
numerical results show that the two solitons in a soliton pair can
affect each other through a light-induced current and their coupling
can affect their spatial profiles under the limit in which the
optical wave has a spatial extent much less than the width of the
crystal. 相似文献
2.
Quasistable bright dissipative holographic solitons in photorefractive two-wave mixing system
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The dynamical evolution of both signal and pump beams are traced
by numerically solving the coupled-wave equation for a
photorefractive two-wave mixing system. The direct simulations
show that, when the intensity ratio of the pump beam to the
signal beam is large enough, the pump beam presents a common
decaying behaviour without modulational instability (MI), while
the signal beam can evolve into a quasistable spatial soliton
within a regime in which the pump beam is depleted slightly. The
larger the ratio is, the longer the regime is. Such quasistable
solitons can overcome the initial perturbations and numerical
noises in the course of propagation, perform several cycles of
slow oscillation in intensity and width, and persist over tens
of diffraction lengths. From physical viewpoints, these solitons
actually exist as completely rigorous physical objects. If the
ratio is quite small, the pump beam is apt to show MI, during
which the signal beam experiences strong expansion and shrinking
in width and a drastic oscillation in intensity, or completely
breaks up. The simulations using actual experimental parameters
demonstrate that the observation of an effectively stable
soliton is quite possible in the proposed system. 相似文献
3.
Effect of temperature on the evolution of bright and dark screening—photovoltaic spatial solitons
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We investigate theoretically the temperature effects on the evolution of both bright and dark screening-photovoltaic optical spatial solitons in biased photovoltaic-photocefractive crystals in the case of neglecting the diffusion process.For a stable bright or dark screening-photovoltaic soliton originally formed in a crystal at a given temperature,when the crystal temperature changes,it will evolve into another stable screening-photovoltaic soliton if the change is quite small,whereas it will become unstable or break down if the temperature change is large enough.The spatial shape of a stable screening-photovoltaic soliton can be reshaped by appropriately adjusting the crystal temperature. 相似文献
4.
This paper investigates the temporal behaviour of open-circuit bright photovoltaic spatial solitons by using numerical techniques. It shows that when the intensity ratio of the soliton, the ratio between the soliton peak intensity and the dark irradiance, is small, the quasi-steady-state soliton width decreases monotonically with the increase of τ-, where τ- is the parameter correlated with the time, that when the intensity ratio of the soliton is big, the quasi-steady-state soliton width decreases with the increase of τ- and then increases with τ, and that the formation time of the steady-state solitons is not correlated with the intensity ratio of the soliton. It finds that the local nonlinear effect increases with the photovoltaic field, which behaves as that the width of soliton beams is small and the self-focusing quasi-period is short. On the other hand, we also discuss that both the time and the temperature have an effect on the beam bending. 相似文献
5.
Diffusion-induced deflection and the effect of two-wave mixing gain on dissipative photovoltaic solitons 总被引:1,自引:0,他引:1
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In an open-circuit dissipative photovoltaic (PV) crystal, by
considering the diffusion effect, the deflection of bright
dissipative photovoltaic (DPV) solitons has been investigated by
employing numerical technique and perturbational procedure. The
relevant results show that the centre of the optical beam moves along
a parabolic trajectory, while the central spatial-frequency component
shifts linearly with the propagation distance; furthermore, both the
spatial deflection and the angular derivation are associated with the
photovoltaic field. Such DPV solitons have a fixed deflection degree
completely determined by the parameters of the dissipative system.
The small bending cannot affect the formation of the DPV soliton via
two-wave mixing. 相似文献
6.
Solitary Wave Evolution of Optical Planar Vortices in Self-Defocusing Photorefractive Media
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Solitary wave evolution of optical planar vortices in isotropie self-defoeusing photorefractive media is investigated in detail. We demonstrate that the formation of a planar vortex soliton intensively depends on the diameter and maximum intensity of the input vortex Seam. The exact solutions of planar vortex solitons are obtained due to the Petviashvili iteration method. It is found that, with the increasing soliton maximum intensity, the soliton core will be gradually diminished to a minimum value. 相似文献
7.
Spatial beam shaping by quartz crystal piano-convex lens 总被引:1,自引:0,他引:1
Based on the optical activity of quartz crystal, we proposed a scheme for shaping the spatial intensity distribution of a linearly polarized laser beam by utilizing a quartz crystal piano-convex lens in combination with a polarizer. The intensity profile of the shaped laser beam can be easily switched from one profile to another by controlling the polarization direction of the incident laser beam. 相似文献
8.
Incoherent interaction between one- and two-dimensional solitons in noncentrosymmetric photorefractive media
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The incoherent interaction between solitons with different
transverse dimensions in a noncentrosymmetric photorefractive
crystal is studied both in theory and in experiment. An anomalous
incoherent interaction between one- and two-dimensional solitons,
whose attractive and repulsive effects depend on the soliton
separation, is numerically demonstrated by employing an anisotropic
model. By launching a one-dimensional green beam and a
two-dimensional red beam into a biased SBN:60 crystal, the
hybrid-dimensional soliton interaction is performed. The
experimental results are in good agreement with the numerical
ones. 相似文献
9.
《中国光学快报(英文版)》2008,(8)
Based on the optical activity of quartz crystal,we proposed a scheme for shaping the spatial intensity distribution of a linearly polarized laser beam by utilizing a quartz crystal piano-convex lens in combination with a polarizer.The intensity profile of the shaped laser beam can be easily switched from one profile to another by controlling the polarization direction of the incident laser beam. 相似文献
10.
We report the numerical observation of discrete spatial solitons in a periodically poled lithium niobate waveguide array by applying an electrical field through electro-optical effect. We show that discrete spatial soliton can be controlled by applied voltage in the periodically poled lithium niobate. 相似文献
11.
Two-Dimensional Photovoltaic Dark Spatial Solitons of Partially Spatially Incoherent Light
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We report a successful experimental observation of two-dimensional photovoltaic dark solitons in an anisotropic crystal with partially spatially incoherent light beams. This kind of solitons results from the bulk photovoltaic effect, which depends on the direction of propagation of the optical beam and on the orientation of the intensity gradient, with respect to the principal axes of the crystal 相似文献
12.
We demonstrate our experiment of controlling spatial displacements of the probe beam induced by the cross-Kerr effect in a three-level V-type atomic system. By increasing the atomic density or the intensity of strong control laser beams, spatial displacements are enhanced. We further study the difference of effects from the atomic density and the laser intensity. In addition, the spatial displacement efficiencies of the probe beam in different energy level atomic systems are compared. Such studies of controlling spatial displacements can have potential applications in soliton deflection, spatial optical switch and generating spatially correlated (entangled) laser beams in multi-level EIT systems. 相似文献
13.
Self-deflection of a bright soliton in a separate bright-dark spatial soliton pair based on a higher-order space charge field
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The self-deflection of a bright solitary beam can be controlled by a dark solitary beam via a parametric coupling effect between the bright and dark solitary beams in a separate bright-dark spatial soliton pair supported by an unbiased series photorefractive crystal circuit. The spatial shift of the bright solitary beam centre as a function of the input intensity of the dark solitary beam (\hatρ) is investigated by taking into account the higher-order space charge field in the dynamics of the bright solitary beam via both numerical and perturbation methods under steady-state conditions. The deflection amount (Δs_0), defined as the value of the spatial shift at the output surface of the crystal, is a monotonic and nonlinear function of \hatρ. When \hatρ is weak or strong enough, Δs_0 is, in fact, unchanged with \hatρ, whereas Δs_0 increases or decreases monotonically with \hatρ in a middle range of \hatρ. The corresponding variation range (δs) depends strongly on the value of the input intensity of the bright solitary beam (r). There are some peak and valley values in the curve of δs versus r under some conditions. When \hatρ increases, the bright solitary beam can scan toward both the direction same as and opposite to the crystal's c-axis. Whether the direction is the same as or opposite to the c-axis depends on the parameter values and configuration of the crystal circuit, as well as the value of r. Some potential applications are discussed. 相似文献
14.
It is numerically proven that dissipative holographic solitons, which are proposed for biased photorefractive materials when the self-trapping beam couples coherently with a pump beam via two-wave mixing, can exist when the intensity of the self-trapping beam is comparable with or stronger than that of the pump beam. Based on the mechanism of forming the soliton, an approach is established used to find the numerical solutions of the soliton. Such numerical solutions have been found for a broad range of system parameters. An experimental way to find such solitons is proposed. 相似文献
15.
Fundamental and dressed annular solitons in saturable nonlinearity with parity–time symmetric Bessel potential
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We theoretically study the existence and stability of optical solitons in saturable nonlinearity with a two-dimensional parity–time(PT) symmetric Bessel potential.Besides the fundamental solitons,a novel type of dressed soliton,whose intensity looks like a ring dressed on an intensity hump,are presented.It is found that both the fundamental solitons and dressed solitons can exist when the propagation constant is beyond a certain critical value.The propagation stability is investigated with a linear stability analysis corroborated by a beam propagation method.All the fundamental solitons are stable,while dressed solitons are unstable for low values of saturable parameter.As the value of saturable parameter increases,the dressed solitons tend to be stable at high powers. 相似文献
16.
This paper predicts that grey spatial solitons can exist in
two-photon photorefractive materials. In steady state and under
appropriate external bias conditions, it obtains the grey spatial
soliton solutions of the optical wave evolution equation. The
intensity profile, phase distribution,and transverse velocity of
these grey solitons are discussed. 相似文献
17.
We study analytically and numerically the propagation of spatial solitons in a two-dimensional strongly nonlocal nonlinear medium. Exact analytical solutions in the form of self-similar spatial solitons are obtained involving higher-order Hermite-Gaussian functions. Our theoretical predictions provide new insights into the low-energy spatial soliton transmission with high fidelity. 相似文献
18.
Temperature effect on dissipative holographicscreening-photovoltaic solitons in a biased dissipative system
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In a biased dissipative photovoltaic-photorefractive system, this paper investigates the temperature effect on the evolution and the self-deflection of the dissipative holographic screening-photovoltaic (DHSP) solitons. The results reveal that, the evolution and the self-deflection of the bright and dark DHSP solitons are influenced by the system temperature. At a given temperature, for a stable DHSP soliton originally formed in the dissipative system, it attempts to evolve into another DHSP soliton when the temperature change is appropriately small, whereas it will become unstable or break down if the temperature departure is large enough. Moreover, the self-deflection degree of the solitary beam centre increases as temperature rises in some range, while it is decided by the system parameters and is slight under small-signal condition. The system temperature can be adjusted to change the formation and the self-deflection of the solitary beam in order to gain certain optical ends. In a word, the system temperature plays a role for the DHSP solitons in the dissipative system. 相似文献
19.
The temporal property of grey screening spatial solitons due to two-photon photorefractive effect in lowamplitude regime is analyzed. The results indicate that a broad solitons is generated at the beginning, and as time evolves, the intensity width of grey solitons decreases monotonically to a minimum value toward steady state. In the same propagation time, the FWHM of solitons decreases with p increasing or m decreasing. Moreover, the formation time of solitons is independent of p and m. The time is close to a constant determined by the dielectric relaxation time. 相似文献
20.
We investigate the properties of waveguides induced by one-dimensional grey
screening solitons in biased photorefractive crystals. The results show that
waveguides induced by grey screening solitons are always of single mode for all
intensity ratios, i.e. the ratios between the peak intensity of the
soliton and the dark irradiance. Our analysis indicates that the
energy confined near the centre of the grey soliton and the propagation constant of
the guided mode of the waveguide induced by the grey screening soliton
increase monotonically with intensity ratio increasing. On the other hand,
when the soliton greyness increases, the energy confined near the centre
of the grey soliton and the propagation constant of the guided mode of the
waveguide induced by the grey screening soliton decrease monotonically.
Relevant examples are provided where photorefractive crystal is of the
strontium barium niobate type. 相似文献