טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentSchwartz Tal
SubjectNonlinear Dynamics and Effects in Optical Systems
DepartmentDepartment of Physics
Supervisor ? 18? Mordechai Segev
Full Thesis textFull thesis text - English Version


Abstract

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.