TUTCRIS - Tampereen teknillinen yliopisto

TUTCRIS

Tunable self-focusing and self-steering of nematicons

Tutkimustuotosvertaisarvioitu

Yksityiskohdat

AlkuperäiskieliEnglanti
Otsikko2011 Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference, CLEO EUROPE/EQEC 2011
DOI - pysyväislinkit
TilaJulkaistu - 2011
OKM-julkaisutyyppiA4 Artikkeli konferenssijulkaisussa
Tapahtuma2011 Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference, CLEO EUROPE/EQEC 2011 - Munich, Saksa
Kesto: 22 toukokuuta 201126 toukokuuta 2011

Conference

Conference2011 Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference, CLEO EUROPE/EQEC 2011
MaaSaksa
KaupunkiMunich
Ajanjakso22/05/1126/05/11

Tiivistelmä

Nematicons, i.e., optical spatial solitons in nematic liquid crystals (NLC), have been attracting a great deal of attention due to their unique properties such as, for example, excitability at powers of a few hundred μW and the possibility to be electrically and/or optically (by other light beams) bent.[1] In this work we investigate, both experimentally and theoretically, the nematicon behavior for different degrees of nonlinearity, discussing how the latter affects the beam width (self-focusing) and trajectory (self-steering). Having defined the angle between the molecular director n (i.e., the local optic axis) and the beam wavevector k = n0k0 z (k0 is the vacuum wavenumber, n0 the linear refractive index), the propagation of the extraordinary wave in the plane yz in a homogeneous NLC cell of thickness L across x is ruled by the equivalent 2D model [2,3] equation equation where is the beam magnetic field and is the all-optical perturbation on , with 0 being the unperturbed , i.e., 0 = (F = 0). In Eqs. (1-2), Dy is the diffraction coefficient along y, (b) the walk-off of the soliton, = [0/(4K)](n2 n 2)[Z0/(n0 cos)]2, and n e 2 is the nonlinear change in the extraordinary refractive index ne. Eq. (2) is a reorientational equation which allows to compute the dielectric properties of the medium ( and ne) once it is known the torque exerted by light on the NLC molecules, whereas (1) determines the beam profile once the n-distribution is known. It is clear from Eq. (2) that the nonlinear response, determined by the optical torque, depends on the initial angle 0: hence, by changing 0 it is possible to easily modify the nonlinear response of the sample, the latter feasible via an applied bias in a planar cell with interdigitated comb-like electrodes. [3] In the limit 0, using Eqs. (1-2) it is possible to define two scalar parameters to investigate self-focusing (ruled by ne 2) and self-steering (determined by ) versus 0: a nonlocal Kerr coefficient n2, given by n2(0) = 2sin[2( 0)]ne 2(0) tan, and equation, proportional to the sensitivity of to the light intensity (Fig. 1), respectively. Numerical simulations of Eqs. (1-2) via BPM confirm the soliton behavior versus 0 (Fig. 1). Figure 1 also shows the corresponding experimental results, with an excellent agreement with the theoretical predictions.

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