Spatial Optical Solitons Research Articles

Large phase shift of spatial soliton in lead glass by cross-phase modulation in pump-signal geometry

We investigate the co-propagation of a strong pump beam and a weak signal beam in lead glass, and find that the large phase shift of the strongly nonlocal spatial optical soliton (SNSOS) can be realized via cross-phase modulation. The theoretical study suggests a synchronous propagation of the pump SNSOS and the signal SNSOS under the required initial condition. A π-phase shift of the signal SNSOS is experimentally obtained by changing the power of the pump SNSOS by about 13 mW around the soliton critical power, which agrees qualitatively with our theoretical prediction. The ratio of the phase shift rate of the signal SNSOS to that of the pump SNSOS shows a close match to the reciprocal of the ratio between their wavelengths.

Vortex confinement and bending with nonlocal solitons

We investigate the routing of vortex beams in nonlocal media by means of coaxial, co-propagating spatial optical solitons. By introducing a refractive index perturbation in the form of a localized defect or a dielectric interface, the soliton waveguide can be curved and, therefore, can deviate the collinear vortex, effectively routing it, while preventing its destabilization and breakup.

Theoretical investigation of spatial optical solitons in nematic liquid crystals with negative dielectric anisotropy

In this paper, the nonlocal nonlinear medium, nematic liquid crystals (NLCs) with negative dielectric anisotropy, are studied. Theoretical research shows that NLCs with negative dielectric anisotropic have a negative nonlinear coefficient. The analytical expressions for characteristic length of the nonlocal response function and for nonlinear coefficient are given. Secondly, the solutions for spatial optical solitons in NLCs with negative dielectric anisotropic are obtained by numerical computation. Finally, the influences of beam power and bias voltage on the propagation of the beam in NLCs with negative dielectric anisotropic are investigated. The result shows that the critical power of the nonlocal spatial solitons in NLCs with negative dielectric anisotropic varies with bias voltage.

Potential formalism of optical spatial soliton propagation in a two-photon photovoltaic–photorefractive material under open circuit condition

Propagation characteristics of optical spatial solitons in a two-photon photovoltaic–photorefractive medium under open circuit condition have been investigated using the formalism of a particle in a potential well. Optical nonlinearity has been evaluated using Castro-Camus model. Variational formalism has been employed to investigate the resulting modified nonlinear Schrodinger equation. Potential formalism has been examined to identify localized optical spatial solitons.

Aging solitons in photorefractive dipolar glasses

We study experimentally the aging of optical spatial solitons in a dipolar glass hosted by a nanodisordered sample of photorefractive potassium-sodium-tantalate-niobate (KNTN). As the system ages, the waves erratically explore varying strengths of the nonlinear response, causing them to break up and scatter. We show that this process can still lead to solitons, but in a generalized form for which the changing response is compensated by changing the normalized wave size and intensity so as to maintain fixed the optical waveform.

Nematicons deflection through interaction with disclination lines in chiral nematic liquid crystals

In this work, we study experimentally the interaction of spatial optical soliton in chiral nematic liquid crystals with disclination line created in a wedge shaped cell. We show that in most cases the self-confined beam preserves this interaction. We demonstrate that this interaction can be employed for efficient bending of the soliton trajectory, as a result of reflection and refraction.

Soliton switching in inhomogeneous nonlocal media

We address a simple way to achieve routing of optical spatial solitons via soliton interactions in the inhomogeneous nonlocal media. We reveal that the variation of the nonlocality disturbs the solitons pairs and splits them into two individual solitons which have the same escape angle but opposite deflection directions. In particular, the escape angle monotonically increases with the increase of the nonlocality variation rate. We demonstrate that the soliton pairs could form self-consistent waveguides that are able to controllably guide a weak signal by any output positions.

The formation and transformation of the spatial weak-light bright and dark solitons in a quantum dot molecule with the interdot tunneling coupling

We study analytically the properties of the optical absorption and the spatial weak-light solitons in a quantum dot molecule system with the interdot tunneling coupling (ITC). It is shown that, for the linear case, there exists tunneling induced transparency (TIT) in the context of a weak ITC, while the TIT can be replaced by Autler-Townes splitting in the presence of a strong ITC. For the nonlinear case, it is probable to realize the spatial optical solitons even under weak light intensity. Interestingly, we find that there appears transformation behavior between the bright and dark solitons by properly turning both the ITC strength and the detuning of the probe field. Meanwhile, the transformation condition of the bright and dark solitons is obtained. Additionally it is also found that the amplitude of the solitons first descends and then rises with the increasing of ITC strength. Our results may have potential applications for nonlinear optical experiments and optical telecommunication engineering in solid systems.

Spiraling elliptic solitons in nonlocal nonlinear media without anisotropy

The spatial optical solitons with ellipse-shaped spots have generally been considered to be a result of either linear or nonlinear anisotropy. We investigate a class of spiraling elliptic solitons in nonlocal nonlinear media without both linear and nonlinear anisotropy. The spiraling elliptic solitons carry the orbital angular momentum (OAM), which plays a key role in the formation of such solitons, and are stable for any degree of nonlocality except the local case if the response function is Gaussian. During the propagation of such solitons, the rate of decay of the OAM is extremely low. The formation of such solitons can be attributed to effective anisotropic diffraction (linear anisotropy) resulting from the OAM. Our variational analytical result is confirmed by direct numerical simulation of the nonlocal nonlinear Schr\odinger equation.

Spatial solitons in biased two-photon photorefractive crystals with both the linear and quadratic electro-optic effect

Abstract The evolution equation of one-dimension spatial optical solitons resulting from two-photon effect in biased photorefractive crystals with both the linear and quadratic electro-optic effect is presented theoretically. Under appropriate conditions, our analysis indicates that bright, dark photorefractive spatial solitons can exist in the steady-state regime. The analytical solutions in the low amplitude regime are also obtained. Moreover, we theoretically discuss the self-deflection of bright solitons by taking the diffusion effect into account. Both the self-deflection effects follow a cubic polynomial of the applied bias field, and increase considerably at higher values of applied bias field. Relevant examples are provided.

OPTICAL SPATIAL SOLITON IN STRONG NONLOCAL LOGARITHMIC MEDIUM

In this paper, the propagation of Gaussian beam in strong nonlocal logarithmic medium is studied, and the evolution equations for the parameters are obtained. The initial condition of forming spatial optical soliton in this kind of medium, which requires the initial beam on-waist incident and its width equaling to the critical beam width, is different from that in strong nonlocal Kerr medium. The reason of the difference is also analyzed. Moreover, the result shows that the beam width will oscillate periodically when the initial condition is dissatisfied. In addition, we discuss the influence of the initial beam width on oscillating range.

Properties of optical spatial solitons in photorefractive crystals with special emphasis to two-photon photorefractive nonlinearity

We have reviewed recent developments of some aspects of optical spatial solitons in photorefractive media. Underlying principles governing the dynamics of photorefractive nonlinearity have been discussed using band transport model. Nonlinear dynamical equations for propagating solitons have been derived considering single as well as two-photon photorefractive processes. Fundamental properties of screening and photovoltaic solitons have been considered. For each type of solitons, three different configurations i.e., bright, dark and gray varieties have been considered. Mechanisms of formation of these solitons due to single as well as two-photon photorefractive processes have been considered and their self bending discussed. Vector solitons, particularly, incoherently coupled solitons due to single photon and two-photon photorefractive phenomena have been highlighted. Existence of some missing solitons have been also pointed out. In addition, incoherent solitons and discrete spatial solitons in optically-induced photorefractive lattices are also discussed.

Elastic and inelastic interactions between optical spatial solitons in nonlinear optics

Elastic and inelastic interactions between optical spatial solitons in nonlinear optics, which to our knowledge have not been reported before, are investigated in this paper. Analytic soliton solutions for the coupled nonlinear Schrödinger equation are obtained using the Hirota method. The coefficient constraints, which can be used to determine whether the soliton interactions are elastic or inelastic, are presented. With different coefficient constraints, the characteristics of soliton interactions are exhibited. The results of this paper may have applications in the design of directional couplers and all-optical logical gates.

Nonlinear switching with a graphene coupler

We study nonlinear propagation of electromagnetic waves in two closely spaced graphene layers and demonstrate that this double-layer graphene waveguide can operate as an efficient nonlinear optical coupler for both continuous plasmons and for subwavelength spatial optical plasmon solitons. We analyze the nonlinearity-induced effects of light localization and symmetry breaking in such a graphene coupler, and predict that the interlayer power-dependent coupling provides a mechanism for optical beam control and manipulation at realistic input power levels.

Deflection and trapping of spatial solitons in linear photonic potentials

We investigate the dynamics of spatial optical solitons launched in a medium with a finite perturbation of the refractive index. For longitudinally short perturbations of super-Gaussian transverse profile, as the input power varies we observe a transition from a wave-like behavior where solitons break up into multiple fringes to a particle-like behavior where solitons acquire a transverse velocity retaining their shape. For longitudinally long perturbations with an attractive potential solitons get trapped inside the well and propagate with transverse periodic oscillations, resulting in an efficient power-dependent angular steering or deflection. Using the Ehrenfest theorem we derive analytical expressions for soliton trajectory, and achieve excellent agreement between theory and numerical simulations for large powers, that is, narrow solitons.

Spatial optical solitons in fifth order and seventh order weakly nonlocal nonlinear media

We analytically study the (1+1)-dimensional spatial optical solitons in weakly nonlocal nonlinear media with cubic–quintic nonlinearity (fifth order nonlinear media) and cubic–quintic–septic nonlinearity (seventh order nonlinear media). Explicit solutions are derived, which include optical bright solitons, singular solutions and singular triangular periodic solution.

Theory of spatial optical solitons in metallic nanowire materials

I characterize the spatial optical solitons supported by arrays of metallic nanowires embedded in Kerr-type material. The array of nanowires is described using an effective medium model and is regarded as a continuous medium. I show that the conditions necessary for the formation of spatial solitons are radically different in presence of the nanowires. In particular, within the effective medium model, spatial solitons are allowed in the nanowire material only when the host material is a ``self-defocusing'' material. It is proven that the characteristic soliton beamwidth is related to the degree of hyperbolicity of the isofrequency surfaces of the photonic states and that a sufficiently strong electric field amplitude may enable subwavelength solitary waves.

Deflection of nematicons through interaction with dielectric particles

We show that the simple interaction of spatial optical solitons in nematic liquid crystals with dielectric particles preserves in most cases the self-confinement of these robust nonlinear self-trapped beams, also known as nematicons. Employing spherical defects such as air bubbles and glass spheres, we report on the experimental observation of total internal reflection as well as refractive deflection of nematicons, with angular changes as large as nearly 90°. We also show multiple reflections and the interaction of a particle with two counterpropagating nematicons.

Exact solitons in three-dimensional weakly nonlocal nonlinear time-modulated parabolic law media

The three-dimensional (3D) nonlocal nonlinear Schrödinger equation (NNLSE) with time-dependent parabolic law nonlinearity and an external potential, describes the propagation of an optical pulse in the weakly nonlocal nonlinear parabolic law media, has been studied analytically. Explicit solutions are constructed by using the Jacobian elliptic equations (JEEs) expansion method. The 3D nonlocal spatial bright and dark optical solitons have been found.

Cascaded Raman slow light and optical spatial solitons in Kerr media

We provide a complete experimental and numerical investigation of nonlinear beam propagation in a carbon disulfide liquid-filled Kerr slab waveguide using picosecond pulsed light. A first spatial analysis shows the generation of a multicolor solitary wave through the combined effects of cascaded Raman scattering and cross-phase modulation. The impact of temporal effects on this self-trapped optical beam is further studied through a spatiotemporal analysis. It is shown in particular how cascaded Raman slow light induces optical delays between the solitonic components which prevents higher-order spatial soliton and provides a remarkable beam stability. Experimental observations are in very good agreement with numerical simulations of the spatiotemporal (1+1D) nonlinear Schr\"odinger equation including the Raman scattering.