Multifunctional Metasurface Tuning by Liquid Crystals in Three Dimensions.

Optical metasurfaces present remarkable opportunities for manipulating wave propagation in unconventional ways, surpassing the capabilities of traditional optical devices. In this work, we introduce and demonstrate a multifunctional dynamic tuning of dielectric metasurfaces containing liquid crystals (LCs) through an effective three-dimensional (3D) control of the molecular orientation. We theoretically and experimentally study the spectral tuning of the electric and magnetic resonances of dielectric metasurfaces, which was enabled by rotating an external magnetic field in 3D.

Formation and stability of vortex solitons in nematic liquid crystals.

We study the propagation dynamics of bright optical vortex solitons in nematic liquid crystals with a nonlocal reorientational nonlinear response. We investigate the role of optical birefringence on the stability of these solitons. In agreement with recent experimental observations, we show that the birefringence-induced astigmatism can eventually destabilize these vortex solitons.

Optical beaming of electrical discharges.

Igniting and guiding electrical discharges to desired targets in the ambient atmosphere have been a subject of intense research efforts for decades. Ability to control discharge and its propagation can pave the way to a broad range of applications from nanofabrication and plasma medicine to monitoring of atmospheric pollution and, ultimately, taming lightning strikes. Numerous experiments utilizing powerful pulsed lasers with peak-intensity above air photoionization and photo-dissociation have demonstrated excitation and confinement of plasma tracks in the wakes of laser field.

Anomalous interaction of spatial solitons in nematic liquid crystals.

We study experimentally the interaction of mutually incoherent bright spatial solitons in dye-doped nematic liquid crystals (LCs). The dye-induced light absorption results in a complex nonlinear optical response of the LC having spatially nonlocal focusing and defocusing contributions. The competition between both nonlinearities leads to the separation-dependent soliton interaction with repulsion of distant and attraction of closely placed solitons.

Nonlinear propagation and quasi self-confinement of light in plasmonic resonant media.

We study nonlinear propagation of light in colloidal suspension of metallic nanoparticles, in the regime of particles surface plasmon resonance. We show that the propagation exhibits features typical for purely defocusing media and the observed spatial confinement is not a real self-trapping, as for solitons, but rather than is caused by the phase modulation of the beam via nonlocal defocusing nonlinearity. We also show that the light-induced refractive index change in the suspension leads to stabilization of structured light beams.

[The efficacy of cocarnit in diabetic neuropathy].

Aim: To study the efficacy of the complex therapy, including cocarnit (group B vitamins, triphosadenine and nicotinamide), of diabetic neuropathy.

Material And Methods: Forty-one patients with diabetes mellitus type 2 and distal symmetric sensorimotor polyneuropathy were examined. Patients were divided into 2 groups.

Risk Factors for Urinary Retention Following Surgical Repair of Hip Fracture in Female Patients.

Background/objectives: Postoperative urinary retention (POUR) is a common event following surgical procedures. An increase in the number of elderly individuals who undergo hip fracture repair procedures is inevitable due to the aging of population. Postoperative urinary retention is associated with both early (infections, delirium) and late complications (urinary incontinence) of surgery.

Magnetic routing of light-induced waveguides.

Among photofunctional materials that can be employed to control the propagation of light by modifying their properties, soft dielectrics such as nematic liquid crystals (NLCs) stand out for their large all-optical response. Through reorientation, the molecular distribution of NLCs can be modified by the electric field of light, permitting functional operations and supporting self-localized light beams or spatial optical solitons. To date, the generation and routing of such solitons have been limited by the boundary conditions employed to tailor the properties of NLCs in planar cells or capillaries.

Quasi-phase matching via femtosecond laser-induced domain inversion in lithium niobate waveguides.

We demonstrate an all-optical fabrication method of quasi-phase matching structures in lithium niobate (LiNbO) waveguides using a tightly focused femtosecond near-infrared laser beam (wavelength of 800 nm). In contrast to other all-optical schemes that utilize a periodic lowering of the nonlinear coefficient χ by material modification, here the illumination of femtosecond pulses directly reverses the sign of χ through the process of ferroelectric domain inversion. The resulting quasi-phase matching structures, therefore, lead to more efficient nonlinear interactions.

Laser-writing inside uniaxially birefringent crystals: fine morphology of ultrashort pulse-induced changes in lithium niobate.

This work presents a detailed analysis of the morphology of femtosecond laser-induced changes in bulk lithium niobate (LiNbO) - one of the most common host materials in photonics - using second-harmonic generation microscopy and scanning electron microscopy. It is shown that focused linearly polarized near-infrared pulses can produce two or three distinct axially separated regions of modified material, depending on whether the pulse propagation is along or perpendicular to the optical axis. When laser writing in LiNbO is conducted in multi-shot irradiation mode and the focused light intensity is kept near the bulk damage threshold, periodic planar nanostructures aligned perpendicular to the laser polarization are produced inside the focal volume.

Transverse spin angular momentum of tightly focused full Poincaré beams.

We show theoretically that by tightly focusing a full Poincaré beam one can create states of light whose average spin angular momentum (SAM) is purely transverse. Moreover, the transverse SAM is significantly increased if a narrow annular aperture is inserted into the Poincaré beam. In this case the state with transverse SAM can exist over an extremely long distance along the optical axis.

Nonlinear diffraction in orientation-patterned semiconductors.

This work represents experimental demonstration of nonlinear diffraction in an orientation-patterned semiconducting material. By employing a new transverse geometry of interaction, three types of second-order nonlinear diffraction have been identified according to different configurations of quasi-phase matching conditions. Specifically, nonlinear Čerenkov diffraction is defined by the longitudinal quasi-phase matching condition, nonlinear Raman-Nath diffraction satisfies only the transverse quasi-phase matching condition, and nonlinear Bragg diffraction fulfils the full vectorial quasi-phase matching conditions.

Visualizing polarization singularities in Bessel-Poincaré beams.

We demonstrate that an annulus of light whose polarization is linear at each point, but the plane of polarization gradually rotates by π radians can be used to generate Bessel-Poincaré beams. In any transverse plane this beam exhibits concentric rings of polarization singularities in the form of L-lines, where the polarization is purely linear. Although the L-lines are invisible in terms of light intensity variations, we present a simple way to visualize them as dark rings around a sharp peak of intensity in the beam center.

Unveiling the orbital angular momentum and acceleration of electron beams.

New forms of electron beams have been intensively investigated recently, including vortex beams carrying orbital angular momentum, as well as Airy beams propagating along a parabolic trajectory. Their traits may be harnessed for applications in materials science, electron microscopy, and interferometry, and so it is important to measure their properties with ease. Here, we show how one may immediately quantify these beams' parameters without need for additional fabrication or nonstandard microscopic tools.

Optical vault: a reconfigurable bottle beam based on conical refraction of light.

We employ conical refraction of light in a biaxial crystal to create an optical bottle for photophoretic trapping and manipulation of particles in gaseous media. We show that by only varying the polarization state of the input light beam the optical bottle can be opened and closed in order to load and unload particles in a highly controllable manner.

The role of light-induced nanostructures in femtosecond laser micromachining with vector and scalar pulses.

In this article we compare the results of micromachining of fused silica and silicon with tightly focused scalar (viz., circularly and linearly polarized) and vector (viz., azimuthally and radially polarized) femtosecond laser pulses.

Polarization-dependent ablation of silicon using tightly focused femtosecond laser vortex pulses.

We demonstrate experimentally that, in a tight focusing geometry, circularly polarized femtosecond laser vortex pulses ablate material differently depending on the handedness of light. This effect offers an additional degree of freedom to control the shape and size of laser-machined structures on a subwavelength scale.

Optical manipulation of particle ensembles in air.

We demonstrate that airborne light-absorbing particles can be photophoretically trapped and moved inside an optical lattice formed by multiple-beam interference. This technique allows simultaneous three-dimensional manipulation of multiple micro-objects in gases.

Robust trapping and manipulation of airborne particles with a bottle beam.

We demonstrate that micron-sized light-absorbing particles can be trapped and transported photophoretically in air using an optical bottle formed inside the focal volume of a lens with a controlled amount of spherical aberration. This optical fiber-based single beam trap can be used in numerous applications where true 3D manipulation and delivery of airborne micro-objects is required.

Revealing local field structure of focused ultrashort pulses.

We utilize the interaction of tightly focused ultrashort pulses with transparent media to imprint their local polarization in the focal region. In particular, we demonstrate that this technique allows for a subwavelength resolution diagnostic of complex polarization states including the presence of the longitudinal component of the electric field. Moreover, we demonstrate the first ever material ablation with the longitudinal electric field of femtosecond pulses.

Admission Norton scale scores (ANSS) correlate with rehabilitation outcome and length in elderly patients following hip arthroplasty.

We sought to determine if ANSS used for evaluating pressure sore risk also correlate with rehabilitation outcome and length following hip arthroplasty in elderly patients. This was a retrospective study conducted in a geriatric rehabilitation department during 2009. ANSS, admission albumin serum levels, mini-mental state examination (MMSE) scores, discharge walking functional independence measure (FIM) scores, and rehabilitation length were studied.

Natural shaping of the cylindrically polarized beams.

We have experimentally and theoretically shown that the circularly polarized beam bearing a singly charged optical vortex propagating through a uniaxial crystal can be split after focusing into the radially and azimuthally polarized beams in the vicinity of the focal area provided that the polarization handedness and the vortex topological charge have opposite signs.

Materials processing with a tightly focused femtosecond laser vortex pulse.

In this Letter we present the first (to our knowledge) demonstration of material modification using tightly focused single femtosecond laser vortex pulses. Double-charge femtosecond vortices were synthesized with a polarization-singularity beam converter based on light propagation in a uniaxial anisotropic medium and then focused using moderate- and high-NA optics (viz., NA=0.

Giant optical manipulation.

We demonstrate a new principle of optical trapping and manipulation increasing more than 1000 times the manipulation distance by harnessing strong thermal forces while suppressing their stochastic nature with optical vortex beams. Our approach expands optical manipulation of particles into a gas media and provides a full control over trapped particles, including the optical transport and pinpoint positioning of ∼100  μm objects over a meter-scale distance with ±10  μm accuracy.