Propagation of spatial optical solitons in a dielectric with adjustable nonlinearity

Abstract

We investigate spatial optical solitons propagating in a medium with a saturable but adjustable nonlinearity and a fixed degree of nonlocality. We employ nematic liquid crystals in a planar cell with optical properties tuned by an external voltage and solitons excited in the near infrared. We also demonstrate soliton self-bending versus excitation due to nonlinear variations in walk-off. A theoretical model accounting for the longitudinal derivatives is employed to compute the refractive index distribution and is found in excellent agreement with the experimental data

Reply to “Comment on ‘Spatial optical solitons in highly nonlocal media”'

“…A fitting procedure was necessary for two main reasons: i) some experimental parameters were not known (including the role of the NLC/air interface and the effective elastic constant) and ii) the SMM is approximate, with accuracy being worse in voltage-biased than in bias-free cells [2]. In the past several years, relevant improvements have been made in both technology (better control of the input interface, see [9]) and modeling (accounting, e.g., for walkoff [10][11][12]). Our results establish a good quantitative agreement between experimental data and the modified SMM [2], as recently shown in [13].…”

“…This is quite a questionable assumption and affects the results, as the proper way to introduce molecular noise in NLC is to consider noise both in time and in the transverse direction. When longitudinal random changes are applied exclusively to the pre-tilt angle, the consequence is a stochastic modulation of the nonlinearity in the system [12,36].…”

“…On the one hand, this effect does not affect transverse confinement. On the other hand, the change is adiabatic on the wavelength scale, both in typical experiments [12,45] and in numerical simulations [1,46]. Importantly, this needs to be accounted for even when the second derivative of the nonlinear index well along the propagation direction is not considered.…”

Voltage-driven beam bistability in a reorientational uniaxial dielectric

“…(1) through θ. 24 Equations (1)- (2) support the generation of stable nonlocal spatial optical solitons in NLCs, self-confined extraordinarily polarized wavepackets also termed nematicons. 23,25,26 From Eqs.…”

“…(1) and (2), an equivalent nonlocal Kerr coefficient n 2 = 2ϵ 0 ∆ϵ sin(2θ 0 )n 2 e (θ 0 )/(4K) can be derived. 24 Conversely, if the input beam is ordinarily polarized, i.e., electric field and director are perpendicular to one another (with θ 0 = 0 and n e (θ 0 ) = n ⊥ in Eq. (2)), all-optical reorientation-hence light self-localization-is only possible above a threshold excitation, the optical Fréedericksz transition (FT).…”