Propagation Of Spatial Solitons Research Articles

Large nonlocal nonlinear optical response of castor oil

The nonlocal nonlinearity of castor oil was investigated using the Z-scan technique in the CW regime at 514 nm and in femtosecond regime at 810 nm. Large negative nonlinear refractive indexes of thermal origin, thermo-optical coefficients and degree of nonlocality were obtained for both laser excitation wavelengths. The results indicate that the electronic part of the nonlinear refractive index and nonlinear absorption were negligible. Our results suggest that castor oil is promising candidate as a nonlinear medium for several nonlocal optical applications, such as in spatial soliton propagation, as well as a dispersant agent in the measurement of absorptive properties of nanoparticles.

Spatial solitons in liquid-crystal light valves

Liquid-crystal light valves can control the orientation of a nematic layer under the independent or combined action of applied voltage and impinging light intensity; hence, they offer a unique environment for the propagation of spatial optical solitons or nematicons. We demonstrate nematicon excitation, propagation, and steering in photoconductive light valves.

Two-Dimensional Spatial Solitons in Nematic Liquid Crystals

We study the propagation of spatial solitons in nematic liquid crystals, using the self-similar method. Analytical solutions in the form of self-similar solitons are obtained exactly. We confirm the stability of these solutions by direct numerical simulation, and find that the stable spatial solitons can exist in various forms, such as Gaussian solitons, radially symmetric solitons, multipole solitons, and soliton vortices.

Solitons in optical lattices with nonlocal nonlinearity

The propagation of spatial solitons is systematically investigated in nonlocal nonlinear media with an imprinted transverse periodic modulation of the refractive index. Based on the variational principle and the infinitesimal approximation of Maclaurin series expansion, we obtain an analytical solution of such nonlocal spatial solitons and an interesting result that the critical power for such solitons propagation is smaller than that in uniform nonlocal self-focusing media. It is found that there exist thresholds in modulation period and lattice depth for such solitons. A stable spatial soliton propagation is maintained with proper adjustment of the modulation period and the lattice depth.

Ultrafast Four-Wave Optical Parametric Amplification in Transparent Condensed Bulk Media

We present a short overview of recent advances in ultrashort pulse four-wave optical parametric amplification in transparent condensed bulk media with Kerr nonlinearity. Highly efficient (10% to 15% pump-to-signal energy conversion) four-wave optical parametric amplification in water and fused silica is experimentally demonstrated. The amplification process highly benefits from 1-dimensional spatial soliton propagation regime, which sets in under proper combination of cylindrical beam focusing and noncollinear phase matching geometry with millijoule pumping. Under these operating conditions, strong four-wave coupling quenches catastrophic beam break-up and filamentation, and the setup operates reasonably below the damage threshold of the nonlinear medium. The proposed methodology offers a number of advantages as compared to guided-wave configurations in gaseous media.

Elliptic incoherent spatial solitons and their interactions in strongly nonlocal media with an anisotropic nonlocality

We investigate the propagation and interaction of elliptic incoherent spatial solitons (EISS) in strongly nonlocal kerr media with an anisotropic nonlocality based on the coherent density approach. An exact analytical solution of such EISS is obtained; the results show that such EISS can form with both isotropic and anisotropic coherence. Moreover, we find that the interaction properties of EISS are very similar to that of their coherent counterpart. Some numerical examples are presented and pertinent physics features are addressed.

Investigation of propagation of spatial soliton in nonlocal nonlinear medium of finite-size

In this paper, we investigate the effect of the boundary of the nonlocal nonlinear medium on the propagation of soliton. On the basic of NNLSE and the Poisson equation, using the Green function approach, we obtain the response function of the lead glass of finite-size, which is a strong nonlocal medium. Starting with the paraxial ray equation, we obtain the analytical solutions of the oscillation trajectory and period of the beam. Comparing the analytical solutions with numerical simulations, we found that our analytical solutions are precise when the point of incidence is not near the boundary of the medium.

Propagation of Spatial Solitons with Nonlinear Kerr Effect in Thermal Medium

In this paper, the propagation and behavior of spatial solitons of inho- mogeneous nonlinear Schrodinger equation in thermal medium will be in- vestigated analytically. The theoretical model is established by considering the change of refractive index of medium due to heat deposition of entrance beam. The soliton like solution in such thermal medium was derived. The efiect of input pump power and beam radius on the behavior of solitons will be studied flnally.

Scattering of Spatial Optical Solitons by Subwavelength Air Holes

Using the finite-difference time-domain method, we model the propagation of spatial optical solitons having two orthogonal electric field vector components, and the scattering of such solitons by compact subwavelength air holes (i.e., abrupt dielectric discontinuities in the direct paths of the solitons). Our propagation and scattering studies assume a realistic glass characterized by a three-pole Sellmeier linear dispersion, an instantaneous Kerr nonlinearity, and a dispersive Raman nonlinearity. An unexpected spatial soliton scattering phenomenon is observed: the coalescence of the scattered electromagnetic field into a propagating lower-energy spatial soliton at a point many tens of wavelengths beyond the scattering air hole. Overall, our computational technique is general, and should permit future investigations and design of devices exploiting spatial soliton interactions in background media having submicrometer air holes and dielectric and metal inclusions.

Propagation of optical spatial solitons in finite-size media: interplay between nonlocality and boundary conditions

We study the propagation of spatial solitons close to the lateral boundaries of self-focusing nonlocal media. Using the Green function approach, we investigate the soliton induced index distribution and resulting trajectories in four cases of physical relevance.

Compensation of the influence of loss for a spatial soliton in a dissipative modulated Bessel optical lattice

Propagation of a spatial soliton in a dissipative modulated Bessel optical lattice is investigated, both analytically and numerically. The dynamic evolution equations for beam width, amplitude, and curvature wavefront are obtained by a variational approach. It is shown that by properly increasing the modulation depth of refractive index of the optical lattice, the loss effect can be compensated exactly to fulfill a stable spatial soliton propagation.

Effect of optical activity on propagation of two-dimensional spatial solitons in cubic photorefractive crystals

The self-focusing of two-dimensional Gaussian beams in cubic photorefractive optically active crystals of the (1̄1̄0) cut in the external electric field arbitrarily oriented in the cut plane is theoretically studied. The ranges of orientation of the external electric field are found in which the divergence of the light beam is smaller than the diffraction divergence. The dependences illustrating the existence of two-dimensional spatial solitons in a 15-mm-thick Bi12SiO20 crystal are constructed taking into account the optical activity or neglecting it. The shape of a light beam propagating in the crystal is determined.

Spatial optical solitons in inhomogeneous elliptic core saturating nonlinear fiber

We have investigated the propagation characteristics of spatial optical solitons in saturating nonlinear waveguide employing JWKB and paraxial ray approximation. We have obtained two second-order coupled nonlinear differential equations for transverse soliton widths of solitons. Threshold power for stable propagation of the beam has been calculated from these coupled equations. We have undertaken stability analysis, which predicts robustness of these solitons. Both guiding as well as antiguiding cases have been considered and shown that stable spatial soliton propagation is possible in both cases.

ROUTING LIGHT AT WILL

We present a comprehensive review on the routing of self-confined light-beams in liquid crystals, i.e., generation, propagation and angular steering of self-induced waveguides or spatial solitons in a nonlinear non local dielectric with a large electro-optic response. We describe all-optical routing through soliton-soliton or soliton-beam interactions, as well as voltage-controlled steering in an anisotropic geometry via birefringence or refraction/reflection at a graded interface.

Theoretical investigation of propagation of nonlocal spatial soliton in nematic liquid crystals

In this paper, we investigate the propagation of the nonlocal optical spatial soliton in undoped nematic liquid crystals. On the basis of Schrdinger-type nonlinear equation and reorientation equation, we not only obtained the analytical expression of spatial soliton but also got the expression of breather in the vicinity of the critical power by use of Guassian trial solution. By comparisons of analytical and numerical simulations, we found that our expressions are more precise than those of C.Conti and G.Assanto. Furthermore,we thoroughly compare the nonlocal model in nematic liquid crystals with the linear model suggested by Snyder and Mitchell.

Efficient four-wave parametric amplification and spatial soliton generation in transparent isotropic medium with Kerr nonlinearity

Efficient four-wave parametric amplification and spatial soliton generation in transparent isotropic medium with Kerr nonlinearity

Tunable refraction and reflection of self-confined light beams

Light filaments or optical spatial solitons are self-confined (non-spreading) beams that originate from the balance between diffraction and self-focusing in nonlinear optical media (those with a response dependent on the level of excitation)1,2,3. Owing to their ability to self-trap as well as to guide weaker signals (even if differing in colour or modulation format) within the waveguides or ‘light-pipes’ they induce, optical spatial solitons could form the basis of future all-optical processing networks4,5. One of the most interesting challenges in soliton propagation and engineering concerns light filaments incident on linear/nonlinear or nonlinear/nonlinear interfaces. Here we report the robust propagation, refraction and reflection of optical spatial solitons at the interface between two regions of a nematic liquid crystal. The ability to independently tune the optical properties of each region enables us to steer the beams by refraction and total internal reflection by as much as −18 and +22 degrees, respectively. Moreover, the extended (nonlocal) and anisotropic response of our system supports polarization healing of the solitons across the interface as well as non-specular filament reflection. Finally, exploiting the inherent and all-optically tunable birefringence, we demonstrate unprecedented nonlinear Goos–Hanchen lateral shifts in excess of 0.5 mm.

The modified propagation equation for TM polarized subwavelength spatial solitons in a nonlinear planar waveguide

The wave equation of TM polarized subwavelength beam propagations in a nonlinear planar waveguide is derived beyond the paraxial approximation. This modified equation contains more higher-order linear and nonlinear terms than the nonlinear Schrödinger equation. The propagation of fundamental subwavelength spatial solitons is numerically studied. It is shown that the effect of the higher nonlinear terms is significant. That is, for the propagation of narrower beam the modified nonlinear Schrödinger equation is more suitable than the nonlinear Schrödinger equation.

Realization of particular liquid crystal cells for propagation and characterization of optical spatial soliton

We report on the design, fabrication process and characterization of liquid crystal cells for investigation of optical spatial solitons. Controlling of the director orientation at the input interface, as well as in the bulk, allows to obtain configurations that can produce distinct optical phenomena in a light beam propagating in the cell. For a particular director configuration, it is possible to produce two waves inside the nematic liquid crystal cell: the extraordinary and the ordinary one. With a different director configuration, the extraordinary wave only is obtained, which propagates inside the cell at an angle of more than 7 degrees with respect to the impinging wave vector direction. Under this peculiar configuration and by applying an external voltage, it is possible to have a good control of the propagation direction of the optical spatial soliton.

Self-healing generation of spatial solitons in liquid crystals

We demonstrate that, in suitably designed cells with undoped nematic liquid crystals, extraordinary-wave spatial solitons can be excited at every applied voltage without adjustments in the input polarization. Their walk-off, hence direction of propagation, is externally controlled over angles as large as 7 degrees. The results pave the way not only to polarization-forgiving generation but also to voltage readdressing of these extraordinary-wave nematicons.