Focusing properties of Gaussian beam with superimposed left-handed and right-handed helical phase fronts

Vector diffraction theory is employed to investigate the focusing properties of the Gaussian beams with superimposed left-handed and right-handed helical phase fronts theoretically. Numerical simulations show that the intensity distribution in focal region can be altered considerably by adjusting topological charge m corresponding to right-handed helix and topological charge n corresponding to left-handed helix. Many novel focal pattern may occur. It was shown that the focal pattern evolves from one intensity peak to multiple intensity peaks with changing the topological charge m and n, and all the intensity peaks form in a circle. As the number of intensity peaks is the sum of m and n, the focal pattern can be controlled through adjusting the topological charge m and n. And in order to show the possible applications of these alterable foci pattern, some optical gradient force distributions were also calculated and illuminated.     

Propagation of rotating elliptical Gaussian beams from right-handed material to left-handed material

By applying the ABCD matrix method, we report the propagating properties of the rotating elliptical Gaussian beams(REGBs) from the right-handed material(RHM) to the left-handed material(LHM). Based on the propagation equation, we obtain the intensity distributions of the REGBs during the propagation. It is found that the rotating direction of the REGBs is opposite in the RHM and the LHM, and the rotation angles tend to be π /2 as the propagation distance is long enough.Then we analyze the relationship between the refractive index and the rotating velocity. Furthermore, the energy flow and the angular momentum(AM) of the REGBs which can rotate are also obtained.     

Rheology of nematic solutions of rodlike chains: Comparison of theory and experiment

The rheological properties of nematic solutions of rodlike polymers are discussed, giving comparisons between theoretical results and certain experiments. Most of the theoretical treatments are based on application of the Leslie-Ericksen constitutive equation. The experimental data considered include distortion in a magnetic field and flow in shearing deformation over a range of shear rate, including rheo-optical observations. In general, it appears that the available theory does not describe a number of the features observed.     

Photonic band gap and defect mode from a layered periodic structure with anisotropic nonmagnetic right-handed and left-handed metamaterials

We demonstrate a photonic band gap (PBG) from a layered periodic structure containing anisotropic nonmagnetic right-handed and left-handed metamaterials whose permittivity elements are partially negative. A set of criteria imposed on materials and structures to realize a PBG is derived, and the transmission spectra are also discussed. When a defect layer is introduced, some unusual properties are found in contrast to that of a defect mode in ordinary PBG structures.     

Anomalous temperature dependence of elastic constants in the nematic phase of binary mixtures made of rodlike and bent-core molecules

We report on two anomalous trends in the temperature dependences of the splay (K11) and bend (K33) elastic constants in the nematic (N) phase of mixtures of compounds with rodlike (R) and bent-core (BC) molecules: As the sample is cooled from the isotropic to N transition point, (i) K33 increases, attains a maximum value and then decreases, and (ii) close to the N to smectic A (SmA) transition point, K11 decreases sharply. At higher temperatures the bow axes of BC molecules are aligned along the director n, strongly favoring a bend distortion of n as the orientational order parameter is increased. Close to the N-SmA transition point the smecticlike short-range order builds up, and the arrow axes of BC molecules are aligned along n, facilitating a splay distortion of n. A simple model calculation brings out the anomalous trend in K33.     

Dynamics of the wave packet in a tunnel-coupled structure consisting of amplifying right-handed and absorbing left-handed media

The dynamics of forward and backward waves in the tunnel-coupled waveguide structure that consists of materials with different signs of real and imaginary parts of refractive indices is analyzed. The expressions for the amplitudes of propagating waves and reflection and transmission coefficients are derived. It is demonstrated that such a structure can be used as a slow-wave structure whose parameters can be controlled using an external magnetic field. The absence of the spontaneous generation of the radiation that propagates in the structure is also demonstrated for the given effective gain, phase mismatch of the interacting modes, and waveguide length.     

Hypermagnetic helicity flux in the nuclei of a new phase in the electroweak phase transition

The dynamics of the magnetic helicity in the electroweak phase transition in the early Universe has been analyzed. It has been shown that the interface surface between the symmetric (hypermagnetic) and broken (Maxwellian) phases serves as a membrane at which the helicity is separated. If the number of knots of the hyper-magnetic field is negative, the helicity accumulated in the Maxwellian phase is left-handed.     

Chiral phase transition from the Dyson-Schwinger equations in a finite spherical volume

Within the framework of the Dyson-Schwinger equations and by means of Multiple Reflection Expansion,we study the effect of finite volume on the chiral phase transition in a sphere, and discuss in particular its influence on the possible location of the critical end point(CEP). According to our calculations, when we take a sphere instead of a cube, the influence of finite volume on phase transition is not as significant as previously calculated. For instance,as the radius of the spherical volume decreases from infinite to 2 fm, the critical temperature T c, at zero chemical potential and finite temperature, drops only slightly. At finite chemical potential and finite temperature, the location of CEP shifts towards smaller temperature and higher chemical potential, but the amplitude of the variation does not exceed 20%. As a result, we find that not only the size of the volume but also its shape have a considerable impact on the phase transition.     

Focusing and phase compensation of paraxial beams by a left-handed material slab

On the basis of angular spectrum representation, a formalism describing paraxial beams propagating through an isotropic left-handed material (LHM) slab is presented. The treatment allows us to introduce the ideas of beam focusing and phase compensation by LHM slab. Because of the negative refractive index of LHM slab, the inverse Gouy phase shift and the negative Rayleigh length of paraxial Gaussian beam are proposed. It is shown that the phase difference caused by the Gouy phase shift in right-handed material (RHM) can be compensated by that caused by the inverse Gouy phase shift in LHM. If certain matching conditions are satisfied, the intensity and phase distributions at object plane can be completely reconstructed at the image plane.     

Optical shuttering action in nematic phase of SMHBLC: observation of a ribbon-like texture

In this study, complexes belonging to supramolecular hydrogen-bonded liquid crystal homologous series are synthesized and characterized. Hydrogen bond is formed between p-n-alkyloxy benzoic acids (nBAO, where n?=?5–11) and chlorobenzoic acid (ClBAO), respectively. The isolated homologues are characterized by various techniques such as polarizing optical microscopic (POM) studies, differential scanning calorimetry (DSC), and Fourier transform–infrared spectroscopy. Based on the POM and DSC studies, the phase diagram has been constructed and discussed. A new smectic ordering, labeled as smectic R, has been characterized, which exhibits a ribbon-like texture. This phase is observed in the complexes pertaining to the higher homologous series. Tilt angle in this phase has been experimentally deduced and the results are fitted to the power law which concurs with the mean-field theory predicted value. Optical shuttering action in the homologue has been detected in the nematic phase and the results are also discussed.     

Liquid crystal formation in suspensions of hard rodlike colloidal particles: direct observation of particle arrangement and self-ordering behavior

We successfully prepared monodisperse, hard rodlike colloidal particles with a wide range of length-to-width ratios (L/W). In their suspensions liquid crystals, or nematic (N) and smectic (Sm) phases, spontaneously appeared. The size of the particles made it possible to directly observe their arrangement and dynamics with an optical microscope. The phase behavior observed exhibited an I (isotropic)-Sm transition for L/W=3.5-8.0 and I-N-Sm transitions for L/W=10-35. In pre-Sm transition regions, lateral clustering of the particles and subsequent layering of the clusters were observed exactly.     

Self-asymmetrization of phase grating profile in a nematic S layer: Partially continuous model

The self-asymmetrization of dynamic phase grating profile in a model medium with properties of nematic liquid crystal, caused by the internal electric field induced in this medium, has been numerically simulated.     

Disclinations in the nematic phase of a magnet with spin 1

Two-dimensional topological defects, spin disclinations, exist for a magnet with spin 1 and strong biquadratic interaction, in which the spin nematic state is realized. The spin disclinations have a nonsingular macroscopic core with a saturated magnetic moment and destroyed nematic order. These singular lines have common features with disclinations in nematic liquid crystals, singular disclinations in antiferromagnets, and magnetic vortices. However, significant differences of their properties from the above-mentioned topological defects also exist. The dynamic properties of a disclination in the spin nematic are characterized by the “freezing in the condensate” and by the gyroscopic force.