26 research outputs found
Soliton dynamics in finite nonlocal media with cylindrical symmetry
The effect of finite boundaries in the propagation of spatial nonlocal solitons in media with cylindrical symmetry is analyzed. Using Ehrenfest's theorem together with the Green's function of the nonlinear refractive index equation, we derive an analytical expression for the force exerted on the soliton by the boundaries, verifying its validity by full numerical propagation. We show that the dynamics of the soliton are determined not only by the degree of nonlocality, but also by the boundary conditions for the refractive index. In particular, we report that a supercritical pitchfork bifurcation appears when the boundary condition exceed a certain threshold value
A method to generate complex quasi-nondiffracting optical lattices
We put forward a powerful technique that allows generating
quasi-non-diffracting light beams with a variety of complex transverse shapes
and topologies. We show that, e.g., spiraling patterns, patterns featuring
curved or bent bright stripes, or patterns featuring arbitrary combinations of
harmonic, Bessel, Mathieu and parabolic beams occupying different domains in
the transverse plane can be produced. The quasi-non-diffracting patterns open
up a wealth of opportunities for the manipulation of matter and optical waves,
colloidal and living particles, with applications in biophysics, and quantum,
nonlinear and atom optics.Comment: 14 pages, 6 figures, to appear in Physical Review Letter
Stripe-like quasi-nondiffracting optical lattices
We introduce stripe-like quasi-nondiffracting lattices that can be generated
via spatial spectrum engineering. The complexity of the spatial shapes of such
lattices and the distance of their almost diffractionless propagation depend on
the width of their ring-like spatial spectrum. Stripe-like lattices are
extended in one direction and are localized in the orthogonal one, thereby
creating either straight or curved in any desired fashion optically-induced
channels that may be used for optical trapping, optical manipulation, or
optical lattices for quantum and nonlinear optics applications. As an
illustrative example, here we show their potential for spatial soliton control.
Complex networks consisting of several intersecting or joining stripe-like
lattices suited to a particular application may also be constructed.Comment: 6 pages, 4 figures, to appear in Optics Expres
Soliton dynamics in finite nonlocal media with cylindrical symmetry
The effect of finite boundaries in the propagation of spatial nonlocal solitons in media with cylindrical symmetry is analyzed. Using Ehrenfest's theorem together with the Green's function of the nonlinear refractive index equation, we derive an analytical expression for the force exerted on the soliton by the boundaries, verifying its validity by full numerical propagation. We show that the dynamics of the soliton are determined not only by the degree of nonlocality, but also by the boundary conditions for the refractive index. In particular, we report that a supercritical pitchfork bifurcation appears when the boundary condition exceed a certain threshold value
The choice of idols from a social psychological perspective
The study of adolescents’ idols has an over 100-year tradition. The meta-analysis of Teigen, Normann, Bjorkheim and Helland (2000) showed that idols, which are commonly understood as role models, changed over the last century which is attributed to changes in the social context. The present paper argues that Social Identity Theory (Tajfel & Turner, 1979, 1986) offers an appropriate theoretical framework to conceptualize social context by hypothesising a functional relationship between idols and identity management strategies moderated by the status position of the adolescent’s group s/he belongs to. The hypothesised functional relationship was tested in two studies with white and black adolescent South Africans. The results of the two studies supported our assumptions that the functional relationship between idols and identity management strategies is indeed moderated by status position. The results also indicate that Social Identity Theory seems to be an appropriate theoretical framework when social context is particularly conceptualised as social change
Stable rotating dipole solitons in nonlocal optical media
We reveal that nonlocality can provide a simple physical mechanism for
stabilization of multi-hump optical solitons, and present the first example of
stable rotating dipole solitons and soliton spiraling, known to be unstable in
all types of realistic nonlinear media with local response.Comment: 3 pages, 3 figure
Generation of arbitrary complex quasi-non-diffracting optical patterns
Due to their unique ability to maintain an intensity distribution upon
propagation, non-diffracting light fields are used extensively in various areas
of science, including optical tweezers, nonlinear optics and quantum optics, in
applications where complex transverse field distributions are required.
However, the number and type of rigorously non-diffracting beams is severely
limited because their symmetry is dictated by one of the coordinate system
where the Helmholtz equation governing beam propagation is separable. Here, we
demonstrate a powerful technique that allows the generation of a rich variety
of quasi-non-diffracting optical beams featuring nearly arbitrary intensity
distributions in the transverse plane. These can be readily engineered via
modifications of the angular spectrum of the beam in order to meet the
requirements of particular applications. Such beams are not rigorously
non-diffracting but they maintain their shape over large distances, which may
be tuned by varying the width of the angular spectrum. We report the generation
of unique spiral patterns and patterns involving arbitrary combinations of
truncated harmonic, Bessel, Mathieu, or parabolic beams occupying different
spatial domains. Optical trapping experiments illustrate the opto-mechanical
properties of such beams.Comment: 11 pages, 7 figures, to be published in Optics Expres
Azimuthons in nonlocal nonlinear media
We demonstrate that spatial nonlocal response provides
an effective physical mechanism for stabilization of recently introduced
azimuthally modulated self-trapped rotating singular optical beams or
azimuthons [see A. S. Desyatnikov, A. A. Sukhorukov, and Yu. S. Kivshar,
Phys. Rev. Lett. 95, 203904 (2005)].We find that stable azimuthons become
possible when the nonlocality parameter exceeds a certain threshold value
and, in a sharp contrast to local media, the azimuthons with N peaks can
also exist for N < 2m, where m is the azimuthon topological charge