Escaping Solitons from a Trapping Potential

Solitons propagating within a confining potential undergo momentum-dependent scattering and eventually escape for large excitations. We experimentally highlight this phenomenon in the presence of a nonperturbative nonlinear response using self-confined light beams in a reorientational medium.

Figure 1

(a) Sketch of the cell. (b) Molecular director (optic axis) and coordinate system.

Figure 2

Applied polarization: the potential difference between the two front electrodes is twice larger than between each front electrode and the ground plane. The corresponding torque can rotate the molecules in the plane $\widehat{t}\widehat{p}$.

Figure 3

Distribution of $\theta$, $\varphi$, low-frequency potential and electric field distribution for $V_1=0.55\mathrm{V}$ and $V_2=-0.55\mathrm{V}$ in a cell with E7.

Figure 4

Particle model: (top) calculated trajectory for various excitations; (bottom) the corresponding concavity ${\partial }^2⟨t⟩/\partial p^2$ of the beam path approaches zero as the power increases (black to gray lines).

Figure 5

Photographs showing the propagation of a soliton in the bias-induced graded-index profile for various optical excitations: at low power, the soliton is trapped in the refractive index well. The dashed bell-shaped curves indicate the transverse distribution of $\varphi$.

Figure 6

Data analysis (averaging over 40 shots): (a) mean soliton path versus input power $P$. At low power, the solitons are scattered, but for $P>15\mathrm{mW}$, the initial momentum permits their escape from the voltage-defined potential. (b) Computed concavity of the soliton path between $p=1700\mu \mathrm{m}$ and $p=2000\mu \mathrm{m}$, i.e., ${\partial }^2⟨t⟩/\partial p^2$, versus input power. The line is a linear fit; standard deviation is $0.6·{10}^{-5}\mu {\mathrm{m}}^{-1}$.