716 research outputs found
A scale to measure consumer’s engagement with social media brand-related content
The purpose of this study is to fill the gap in the literature concerning to the measurement of consumer’s engagement with social media brand-related content (hereafter, CESBC). We introduce empirical evidence for the development and measurement of CESBC scale. The scale is based on the consumer's online brand-related framework and comprises three dimensions: consumption, contribution, and creation. We used qualitative techniques to prepare an initial list of items and tested and validated the CESBC scale with confirmatory factor analysis (CFA). Results (n = 2252) confirmed the three-factor structure of the CESBC and indicated its good psychometric properties
Scattering in and Symmetric Multimode Waveguides: Generalized Conservation Laws and Spontaneous Symmetry Breaking beyond One Dimension
We extend the generalize conservation law of light propagating in a
one-dimensional -symmetric system, i.e., for the
transmittance and the reflectance from the left and right, to a
multimode waveguide with either or symmetry, in which
higher dimensional investigations are necessary. These conservation laws exist
not only in a matrix form for the transmission and reflection matrices; they
also exist in a scalar form for real-valued quantities by defining generalized
transmittance and reflectance. We then discuss, for the first time, how a
multimode -symmetric waveguide can be used to observe spontaneous
symmetry breaking of the scattering matrix, which typically requires tuning the
non-hermiticity of the system (i.e. the strength of gain and loss). Here the
advantage of using a multimode waveguide is the elimination of tuning any
system parameters: the transverse mode order plays the role of the symmetry
breaking parameter, and one observes the symmetry breaking by simply performing
scattering experiment in each waveguide channel at a single frequency and fixed
strength of gain and loss.Comment: 8 pages, 6 figure
Breather Statics and Dynamics in Klein--Gordon Chains with a Bend
In this communication, we examine a nonlinear model with an impurity
emulating a bend. We justify the geometric interpretation of the model and
connect it with earlier work on models including geometric effects. We focus on
both the bifurcation and stability analysis of the modes that emerge as a
function of the strength of the bend angle, but we also examine dynamical
effects including the scattering of mobile localized modes (discrete breathers)
off of such a geometric structure. The potential outcomes of such numerical
experiments (including transmission, trapping within the bend as well as
reflection) are highlighted and qualitatively explained. Such models are of
interest both theoretically in understanding the interplay of breathers with
curvature, but also practically in simple models of photonic crystals or of
bent chains of DNA.Comment: 14 pages, 16 figure
Landau-Zener Tunnelling in Waveguide Arrays
Landau-Zener tunnelling is discussed in connection with optical waveguide
arrays. Light injected in a specific band of the Bloch spectrum in the
propagation constant can be transmitted to another band, changing its physical
properties. This is achieved using two waveguide arrays with different
refractive indices, which amounts to consider a Schr\"odinger equation in a
periodic potential with a step. The step causes wave "acceleration" and thus
induces Landau-Zener tunnelling. The region of physical parameters where this
phenomenon can occur is analytically determined and a realistic experimental
setup is suggested. Its application could allow the realization of light
filters.Comment: 4 pages, 6 figure
Spatiotemporal mode-locking in multimode fiber lasers
A laser is based on the electromagnetic modes of its resonator, which
provides the feedback required for oscillation. Enormous progress has been made
in controlling the interactions of longitudinal modes in lasers with a single
transverse mode. For example, the field of ultrafast science has been built on
lasers that lock many longitudinal modes together to form ultrashort light
pulses. However, coherent superposition of many longitudinal and transverse
modes in a laser has received little attention. The multitude of disparate
frequency spacings, strong dispersions, and complex nonlinear interactions
among modes greatly favor decoherence over the emergence of order. Here we
report the locking of multiple transverse and longitudinal modes in fiber
lasers to generate ultrafast spatiotemporal pulses. We construct multimode
fiber cavities using graded-index multimode fiber (GRIN MMF). This causes
spatial and longitudinal mode dispersions to be comparable. These dispersions
are counteracted by strong intracavity spatial and spectral filtering. Under
these conditions, we achieve spatiotemporal, or multimode (MM), mode-locking. A
variety of other multimode nonlinear dynamical processes can also be observed.
Multimode fiber lasers thus open new directions in studies of three-dimensional
nonlinear wave propagation. Lasers that generate controllable spatiotemporal
fields, with orders-of-magnitude increases in peak power over existing designs,
should be possible. These should increase laser utility in many established
applications and facilitate new ones
Local PT invariance and supersymmetric parametric oscillators
We introduce the concept of local parity-time symmetric (PT) invariance in optical waveguides (or cavity) structures. Starting from a Lagrangian formalism, we establish the connection between light dynamics in these configurations and the seemingly different physics of supersymmetric parametric oscillators. Using this powerful tool, we present analytical solutions for optical beam propagation in local PT-invariant coupled systems and we show that the intensity tunneling between the two channels critically depends on the initial conditions. For unbalanced inputs, symmetric as well as asymmetric power evolution can be observed depending on the excitation channel. On the other hand, under certain physical conditions, our analysis predicts that for a modal PT-symmetric input, a unidirectional fractional phase exchange can take place. Few cases where analytical solutions cease to exist are also investigated numerically. Finally, by exploiting the supersymmetric nature of the oscillator equations, we show that under certain initial conditions, one can obtain the propagation dynamics of field amplitudes that resides on the supersymmetric eigenfunctions of the system-a phenomenon we call resonant propagation
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