All-optical measurement of elastic constants in nematic liquid crystals

In this article we present a new all-optical method to measure elastic constants connected with twist and bend deformations. The method is based on the optical Freedericksz threshold effect induced by the linearly polarized electro-magnetic wave. In the experiment elastic constants are measured of commonly used liquid crystals 6CHBT and E7 and two new nematic mixtures with low birefringence. The proposed method is neither very sensitive on the variation of cell thickness, beam waist or the power of a light beam nor does it need any special design of a liquid crystal cell. The experimental results are in good agreement with the values obtain by other methods based on an electro-optical effect

Dependence of the Third Order Nonlinear Optical Susceptibility on Concentration and Peripheral Substituent of Metallophthalocyanines

Third order nonlinear optical properties of metallophthalocyanines (MPcs) were investigated using degenerate four wave mixing (DFWM) method. We also studied how the replacement of peripheral substituent around the MPcs cores correlates with nonlinear optical properties. Therefore third order nonlinear optical susceptibilities (χ<3>) of MPcs with liquid crystal (MPcs-LC) were investigated. We found that the χ<3> values of MPcs-LC increase in comparison with the corresponding values of MPcs. We supposed that this is caused by the increase of the charge transfer effects and change of the dipole moments of the molecule with the increase of molecules dimension

Optical limiting efficiency of an electroactive bis-iminopyridine ligand and its zinc complex

An electroactive based bis-iminopyridine ligand has been synthesized by a condensation reaction between (4-(6,7-dimethyldithio-tetrathiafulvalene)-aniline) with 2,6-diformylpyridine. The complexation of this ligand with ZnCl2 afforded a tetrahedral neutral Zinc metal complex. Nonlinear optical measurements of these structures have given good results in picosecond regime. The nonlinear absorption of the ligand was significantly enhanced upon complexation with ZnCl2. This prompted us to conduct the experiment of optical limiting at wavelength 532nm. The nonlinear absorption properties of these structures were studied and compared to the reference material C60

Standard and Embedded Solitons in Nematic Optical Fibers

A model for a non-Kerr cylindrical nematic fiber is presented. We use the multiple scales method to show the possibility of constructing different kinds of wavepackets of transverse magnetic (TM) modes propagating through the fiber. This procedure allows us to generate different hierarchies of nonlinear partial differential equations (PDEs) which describe the propagation of optical pulses along the fiber. We go beyond the usual weakly nonlinear limit of a Kerr medium and derive an extended Nonlinear Schrodinger equation (eNLS) with a third order derivative nonlinearity, governing the dynamics for the amplitude of the wavepacket. In this derivation the dispersion, self-focussing and diffraction in the nematic are taken into account. Although the resulting nonlinear $PDE$ may be reduced to the modified Korteweg de Vries equation (mKdV), it also has additional complex solutions which include two-parameter families of bright and dark complex solitons. We show analytically that under certain conditions, the bright solitons are actually double embedded solitons. We explain why these solitons do not radiate at all, even though their wavenumbers are contained in the linear spectrum of the system. Finally, we close the paper by making comments on the advantages as well as the limitations of our approach, and on further generalizations of the model and method presented.Comment: "Physical Review E, in press

Multidimensional quantum solitons with nondegenerate parametric interactions: Photonic and Bose-Einstein condensate environments

We consider the quantum theory of three fields interacting via parametric and repulsive quartic couplings. This can be applied to treat photonic chi((2)) and chi((3)) interactions, and interactions in atomic Bose-Einstein condensates or quantum Fermi gases, describing coherent molecule formation together with a-wave scattering. The simplest two-particle quantum solitons or bound-state solutions of the idealized Hamiltonian, without a momentum cutoff, are obtained exactly. They have a pointlike structure in two and three dimensions-even though the corresponding classical theory is nonsingular. We show that the solutions can be regularized with a momentum cutoff. The parametric quantum solitons have much more realistic length scales and binding energies than chi((3)) quantum solitons, and the resulting effects could potentially be experimentally tested in highly nonlinear optical parametric media or interacting matter-wave systems. N-particle quantum solitons and the ground state energy are analyzed using a variational approach. Applications to atomic/molecular Bose-Einstein condensates (BEC's) are given, where we predict the possibility of forming coupled BEC solitons in three space dimensions, and analyze superchemistry dynamics