Boundary effects on the dynamics of higher-order optical spatial solitons in nonlocal thermal media

Abstract

We study theoretically the propagation of higher-order two-dimensional spatial solitons in optical media with nonlocal thermal nonlinear response. We show that these localized states experience complex dynamics including transformations between solitons of different symmetries which depend strongly on the geometry of a nonlinear sample. Boundaries exert repulsive forces on a soliton and, depending on its initial position relative to the boundaries, we observe transverse motion of a beam as a whole across the sample, effectively facilitating transformations.

Modulation analysis of boundary-induced motion of optical solitary waves in a nematic liquid crystal

“…The initial location of the beam is not at the centre of the cell, y = 0, but is at y = ξ = 5. The nematicon then oscillates about the centre line of the cell, as found in previous work [14,19,20,22]. At z = 2000 the electric field beam is peaked at y = 3.55, while the director beam is peaked at y = 3.24, a little closer to the centre of the cell than the electric field peak.…”

“…This repulsion is a direct consequence of the nonlocal nature of the nematic response, combined with the intricate dependence of the response on the specific properties of the boundaries. In general, boundaries affect not only the position, but also the internal dynamics [20] of more complex soliton of different symmetries [32].…”

“…This latter aspect, i.e. the effect of a nonlocal boundary potential on the propagation of spatial solitons, has been recently addressed with specific reference to thermo-optical and reorientational solitons in glass and in liquid crystals, respectively [16][17][18][19][20]. In this paper we undertake the ambitious task of providing a theoretical background to describe the boundarynematicon interaction, analysing the boundary induced motion of these self-localized beams by means of modulation theory, modelling the problem in one transverse dimension, but extending some of the results to the full two-dimensional scenario.…”

Variational and accessible soliton approximations to multidimensional solitons in highly nonlocal nonlinear media

“…To include interactions between solitons within boundaries, as well the impact of the finite size of the sample, we developed a variational approach (VA) to solitons in nonlinear media with long-range nonlocality, such as NLCs [9], materials with thermal nonlocality [10], photorefractive crystals [11], and Bose-Einstein condensates [12]. Starting from an appropriate ansatz, this approach delivers a stationary solution for the beam amplitude and width, as well as the period of small oscillations about the stationary state.…”

Nonlinearity-mediated soliton ejection from trapping potentials in nonlocal media

“…In materials where diffusion processes are involved, such as thermal media, boundary conditions may strongly impact the dynamics of soliton formation. Boundary effects in thermal media have been exploited for beam steering [16][17][18][19], generation of surface waves [20][21][22], and for the formation of new types of solitons [23]. It should be noted that the model describing light propagation in a finite nematic liquid crystal without a static biasing electric field is mathematically equivalent to the model describing light propagation in a thermal medium; thus, boundary effects in such crystals may also considerably affect the propagation dynamics of light beams [24].…”