טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentBartal Guy
SubjectNonlinear Waves in Periodic Photonic Structures
DepartmentDepartment of Physics
Supervisor ? 18? Mordechai Segev
Full Thesis textFull thesis text - English Version


Abstract

My doctoral research focuses on linear and nonlinear wave dynamics in photonic lattices and other periodic structures. In these systems, the periodicity gives rise to band and gaps in the dispersion relations, and the dynamics are determined by the interplay between transport (dispersion /diffraction) effects and nonlinearity. The phenomena associated with these systems are numerous and include lattice solitons, nonlinear wave mixing, nonlinear energy transfer and more.  My research was carried out in the framework of Nonlinear Optics in systems that are easy to control and manipulate; nevertheless,  the physics underlying these phenomena is universal and applies to all nonlinear periodic systems in nature, e.g., Fluid Dynamics, Matter waves, Plasma Physics, etc.
 My Ph.D. research encompasses primarily the following topics

·        First experimental observation of the extended Brillouin-zone map of photonic lattices and photonic lattices with defects. This observation has led to the invention of a novel technique for mapping out photonic lattices, photonic crystals fibers, or periodic structures in fields beyond optics


·        First experimental observation of Random-phase lattice solitons in any system in nature.

 These are lattice solitons made of incoherent light. We have demonstrated self-trapping of spatially-incoherent beams in nonlinear waveguide array, and showed that the spatial spectrum of such entities is multi-humped. We found out that under self-focusing nonlinearity the modal constituents of such RPLS reside in the normally diffracting regions of the lattice band structure spectrum in momentum space.


·                    First experimental observation of Gap Random-phase lattice solitons; self-localized spatially-incoherent states whose modal constituents lie within a photonic band gap, having  no contribution from modes arising from the semi-infinite gap.


·                    First experimental observation of solitons carrying topological charge ('vortex-ring lattice solitons'), in any system in nature


·                    First experimental observation of  vortex solitons arising from the second band of a 2D lattice; this constitutes the first observation of higher-band solitons in 2D periodic structures.


·        First experimental study of spatial four-wave-mixing in photonic lattices;  we have demonstrated  universal aspects of nonlinear processes in periodic media, such as engineered phase-matching, Bloch-wave folding, and continuous control over the band at which the interaction products emerge.  This work combines one of the main nonlinear optics themes (four-wave-mixing) and the fundamentals of waves propagation in periodic structures (the Floquet-Bloch theory) to demonstrate these new universal ideas.