2,636 research outputs found
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
Interaction-induced localization of anomalously-diffracting nonlinear waves
We study experimentally the interactions between normal solitons and tilted
beams in glass waveguide arrays. We find that as a tilted beam, traversing away
from a normally propagating soliton, coincides with the self-defocusing regime
of the array, it can be refocused and routed back into any of the intermediate
sites due to the interaction, as a function of the initial phase difference.
Numerically, distinct parameter regimes exhibiting this behavior of the
interaction are identified.Comment: Physical Review Letters, in pres
Bistable light detectors with nonlinear waveguide arrays
Bistability induced by nonlinear Kerr effect in arrays of coupled waveguides
is studied and shown to be a means to conceive light detectors that switch
under excitation by a weak signal. The detector is obtained by coupling two
single 1D waveguide to an array of coupled waveguides with adjusted indices and
coupling. The process is understood by analytical description in the
conservative and continuous case and illustrated by numerical simulations of
the model with attenuation.Comment: Phys. Rev. Lett., v.94, (2005, to be published
Crossover from self-defocusing to discrete trapping in nonlinear waveguide arrays
We predict a sharp crossover from nonlinear self-defocusing to discrete
self-trapping of a narrow Gaussian beam with the increase of the refractive
index contrast in a periodic photonic lattice. We demonstrate experimentally
nonlinear discrete localization of light with defocusing nonlinearity by single
site excitation in LiNbO waveguide arrays.Comment: 6 pages, 4 figure
Discrete interband mutual focusing in nonlinear photonic lattices
We study nonlinear coupling of mutually incoherent beams associated with
different Floquet-Bloch waves in a one-dimensional optically-induced photonic
lattice. We demonstrate experimentally how such interactions lead to asymmetric
mutual focusing and, for waves with opposite diffraction properties, to
simultaneous focusing and defocusing as well as discreteness-induced beam
localization and reshaping effects.Comment: 8 pages, 6 figures. To download the associated .avi movie, go to
http://www.rsphysse.anu.edu.au/~crr124/mut_focus
Self-Chaotization in Coupled Optical Waveguides
We consider theoretically two coupled optical waveguides with a varying
barrier height along the waveguides direction. The barrier could be constructed
by the elongated island with a reduced refractive index (which acts as a
potential barrier), such that in the middle region it splits a waveguide into
two weakly coupled parts. It is predicted by numerical simulations and
analytical consideration that the presence of some imperfection of the system
parameters can cause splitting of injected laser beam and one will observe two
intensity maximums at the output, while for small imperfections the input and
output beam intensity distributions will be the same. The switching between two
regimes could be achieved changing spectral width of the beam or refractive
index of the island. This nontrivial effect is explained by possibility of
transitions between the different eigenstates of the system in the region of
large potential barrier heights. The mentioned effect could be used for
all-optical readdressing and filtering purposes
Discrete gap solitons in modulated waveguide arrays
We suggest a novel concept of diffraction management in waveguide arrays and
predict the existence of discrete gap solitons that possess the properties of
both conventional discrete and Bragg grating solitons. We demonstrate that both
the soliton velocity and propagation direction can be controlled by varying the
input light intensity.Comment: 4 pages, 3 figure
Power dependent switching of nonlinear trapping by local photonic potentials
We study experimentally and numerically the nonlinear scattering of wave
packets by local multi-site guiding centers embedded in a continuous dielectric
medium, as a function of the input power and angle of incidence. The extent of
trapping into the linear modes of different sites is manipulated as a function
of both the input power and incidence angle, demonstrating power-controlled
switching of nonlinear trapping by local photonic potentials.Comment: Submitted to Optics Letter
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