Ph.D Thesis

Ph.D StudentOren Cohen
SubjectOptical Spatial Solitons
DepartmentDepartment of Physics
Supervisor Full Professors Segev Mordechai


This thesis deals with optical spatial solitons; stationary wave-packets resulting from a robust balance between the linear tendency of dispersion and the nonlinearity.

The first part describes solitons in systems in which mutually-coherent beams induce a hologram and interact with it. We formulated the theory of coherent interactions between solitons that propagate in opposite directions, and demonstrated experimentally solitons consisting of counter-propagating components. Then, we proposed a new type of soliton, the holographic soliton, which results from the interaction between two beams and the hologram they induce. Inspired by that, we proposed and demonstrated experimentally a new method of waveguiding, grating-mediated waveguiding, which consists of a shallow 1D grating dressed by a bell-shaped (or a trough-shaped) amplitude in the direction normal to the grating wave-vector. This grating guides light in a direction normal to its periodicity.

Another system we studied is random-phase solitons in waveguide arrays. As a first step, we studied a vector soliton whose components originate from different bands. Under the action of self-focusing nonlinearity these components move from normal diffraction regions into the forbidden gaps and become localized. By extending this understanding into incoherent light, we proved the existence of incoherent lattice solitons and showed that they universally posses a multi-humped power spectrum and their intensity and coherence properties conform to the lattice periodicity. Eventually, we have experimentally demonstrated random-phase solitons observing both their self-trapping and local periodicity as well as their multi-humped power spectrum.

Finally, we proposed a new type of incoherent solitons, which occur in instantaneous nonlocal nonlinear media. The mechanism responsible for self-trapping of such incoherent wavepackets is played by the non-local nature of the nonlinearity.