Light Beams In Nonlinear Media Research Articles

Collapse of hybrid vector beam in Rb atomic vapor.

In recent years, many researchers have tried to control and design the collapsing behavior of light beams in nonlinear media. Vector beams coupling with spin and orbit angular momentum freedom have attracted more and more attention. In this Letter, we study the collapse of a hybrid vector beam (HVB) propagating through rubidium atomic vapor. First, the HVB collapses into filaments located at positions with linear polarization. As propagation distance in atomic vapor increases, the locations of the filaments switch from positions with linear polarization to those with circular polarization. In this process, the absorption of the medium plays an important role. Results indicate that the absorption can be used as a degree of freedom to modulate the filamentation. Furthermore, by analyzing the polarization angle of an elliptically polarized position on the transverse plane of the HVB, we demonstrate the evolution of polarization distribution of HVB during propagation. Such results could have application in manipulating other structured beams and could be potentially applied to realize optical switches or logic for information processing.

Dark spatial solitary waves in a cubic-quintic-septimal nonlinear medium

We consider the evolution of light beams in nonlinear media exhibiting nonlinearities up to the seventh order wherein the beam propagation is governed by the cubic-quintic-septimal nonlinear Schr\odinger equation. An exact analytic solution that describes dark solitary wave propagation is obtained, based on a special ansatz. Unlike the well-known $\text{tanh}$-profile dark soliton in Kerr media, the present one has a functional form given in terms of ``${\text{sech}}^{2/3}$''. The requirements concerning the optical material parameters for the existence of this localized structure are discussed. This propagating solitary wave exists due to a balance among diffraction, cubic, quintic, and septimal nonlinearities. We also investigate its stability under initial pertubations by employing numerical simulations. The modulational stability of the continuous-wave background, which supports the dark soliton, is also studied analytically. Collisions between stable dark solitons are finally investigated.

Polarization Shaping for Control of Nonlinear Propagation.

We study the nonlinear optical propagation of two different classes of light beams with space-varying polarization-radially symmetric vector beams and Poincaré beams with lemon and star topologies-in a rubidium vapor cell. Unlike Laguerre-Gauss and other types of beams that quickly experience instabilities, we observe that their propagation is not marked by beam breakup while still exhibiting traits such as nonlinear confinement and self-focusing. Our results suggest that, by tailoring the spatial structure of the polarization, the effects of nonlinear propagation can be effectively controlled. These findings provide a novel approach to transport high-power light beams in nonlinear media with controllable distortions to their spatial structure and polarization properties.

Self-action of the pulsed conical light beam in nonlinear medium

Self-action of the pulsed conical light beam in nonlinear medium

Effect of inhomogeneous optical properties of a nonlinear medium on the propagation of powerful light beams

The propagation of powerful light beams in nonlinear media with the Kerr nonlinearity is considered. The effect of local inhomogeneities on self-focusing of the beams is studied.

Theory of Incoherent Self-Focusing in Biased Photorefractive Media

A theory describing propagation and self-focusing of partially spatially incoherent light beams in nonlinear media is developed. It is shown that this process is effectively governed by an infinite set of coupled nonlinear Schr\odinger-like equations, provided they are initially appropriately weighted with respect to the incoherent angular power spectrum of the source. The particular case of spatially incoherent beam propagation in biased photorefractive media is considered in detail. Numerical simulations indicate that spatial compression as well as self-trapped states are possible under appropriate conditions. Our results are in good agreement with recent experimental observations.

The nonlinear Schrödinger equation with dissipation and the moment method

The moment method is applied to study self-focusing and collapse of light beams in nonlinear media with losses. Approximate analytical expressions for collapse length and minimum losses avoiding collapse are found and compared to the exact ones obtained from numerical simulations of the nonlinear Schrödinger equation.

Spatial soliton deflection mechanism indicated by FD-TD Maxwell's equations modeling

We present first-time calculations from the time-domain vector Maxwell's equations of spatial optical soliton propagation and mutual deflection, including carrier waves, in a 2-D homogeneous Kerr-type nonlinear dielectric. The nonlinear Schrodinger equation predicts that two co-propagating, in-phase spatial solitons remain bound to each other, executing a periodic separation. This disagrees with our new extensively tested finite-difference time-domain (FD-TD) solution of Maxwell's equations. FD-TD shows that co-propagating in-phase spatial solitons become unbound, i.e. diverge to arbitrarily large separations, if the ratio of soliton beamwidth to wavelength is order 1 or less. Not relying upon paraxial approximations or analogies to temporal soliton interactions, FD-TD appears to be a robust means of obtaining detailed models of the interaction of sub-picosecond pulsed light beams in nonlinear media directly in the space-time domain. >

Auto-waveguide propagation and the collapse of spiral light beams in non-linear media

The equation governing the propagation of spiral beams in a non-linear medium is analysed. It is shown that, taking into account the saturation effect, spiral beams have a tube-like structure with a periodicity along the axis of a non-linear autoguide. A critical power is found which it is necessary to exceed in order to give rise to the indicated autoguided regime of the beam propagation. Furthermore, in this work a strict self-similar solution is obtained of a non-linear Schrodinger-type equation that describes the collapse of spiral beams, and a new class of self-similar solutions is found for the case of spherical symmetry.

Self-action of light beams in nonlinear media: soliton solutions

The behaviour of light beams in nonlinear media (self-focussing of optical beams as well as self-modulation and transmission of optical pulses) is considered in the case when the nonlinear polarization contains susceptibilities of third- and fifth-order. The soliton solutions are obtained for the nonlinear equations deduced.