Ph.D Student | Schwartz Tal |
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Subject | Nonlinear Dynamics and Effects in Optical Systems |

Department | Department of Physics |

Supervisor | ? 18? Mordechai Segev |

Full Thesis text |

My doctoral research revolves around investigating various topics in nonlinear optics, concentrating on weakly-correlated stochastic systems. In my research, I used nonlinear optics as a workbench for studying general phenomena in nonlinear dynamics. The ideas explored are universal, and can also be found, for example, in fluid dynamics, matter waves, plasma physics and electrons in solids. My research activities fall under one of the following categories:

· **First experimental observation of Anderson localization in
disordered lattices.** We have observed the transverse localization of light
in a two-dimensional photonic lattice, with disorder super-imposed upon it. We demonstrated
how transport in a photonic lattice becomes diffusive upon the introduction of
disorder, and the cross-over to Anderson localization at strong enough disorder.
We studied the effects of nonlinearity on the localization, and showed that self-focusing
nonlinearity promotes localization.

· **Prediction and theoretical study of multi-band vector lattice
solitons.** We predicted multi-band vector solitons in nonlinear periodic
systems, concentrating on nonlinear photonic lattices. The solitons consist of
two mutually-incoherent optical fields from different bands of the spectrum, bound
together by their jointly-induced potential. Our study paved the way towards
general multi-mode lattice solitons, and laid the basic understanding for the
study of incoherent solitons in periodic structures.

· **First observation of spontaneous pattern formation with incoherent
white light.** We studied experimentally the pattern formation of light which
is both spatially and temporally incoherent. We demonstrated experimentally
several unique effects such as the locking-up of all temporal frequencies into
one common spatial periodicity, and the re-adjustment of the temporal spectrum
during the instability process. Furthermore, I observed that all wavelengths
have the same instability threshold.

· **Theoretical study of pattern formation in an optical cavity with an
incoherent feedback loop.** We analyzed a cavity with an incoherent feedback,
and showed that it exhibits a phase transition at a distinct threshold. This
process is very similar to the lasing threshold in lasers and other critical
phenomena.

· **First observation of spatial solitons in a photorefractive
semiconductor CdZnTe:V.** We demonstrated the formation of solitons in a
semiconductor CdZnTe:V, which has a high mobility, facilitating fast
nonlinearity. We showed that the soliton form at a particular (resonance)
intensity, and that the resonant intensity can be tuned by a background beam.
Using this resonance-tuning, we were able to obtain soliton formation times
which are 5 orders of magnitude shorter than normal photorefractives.