טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentLevi Liad
SubjectWave Transport in Interacting and Disordered Systems
DepartmentDepartment of Physics
Supervisor ? 18? Mordechai Segev
Full Thesis textFull thesis text - English Version


Abstract

In my doctoral thesis, I study both linear and nonlinear effects in optical systems. My research can be divided into three different parts:

The first part of my thesis concentrates on modulation Instability. In my research on this subject I studied numerically the long-range propagation of incoherent waves, following incoherent MI, in non-instantaneous Kerr-type media, and in one spatial dimension. I showed that this integrable classical nonlinear wave system reaches a steady-state (a dynamic equilibrium state), at which the coherence is smaller than the initial coherence, i.e., the disorder within the beam increases to its steady-state value.

My research on this area was summarized in the following published paper:

         Spontaneous pattern formation upon incoherent waves: From modulation-instability to steady-state (Optics Express 2008)

The second part of my thesis concentrates on transport in quasicrystals containing disorder.  In our research on this subject, we studied photonic quasi-lattices containing disorder, and present the first direct experimental observation of disorder-enhanced transport in QCs. We did that by directly imaging wavepackets propagating through a photonic QC containing disorder. We have shown that disorder considerably enhances the transport of wavepackets associated with eigenstates in the proximity of a pseudogap (a sharp reduction in the density of states), the region in which the Fermi energy is found in electronic systems.  

My research on this area was done with Dr. Mikael Rechstman (a post-doc in our group) which equally contributed to this work. It is summarized in the following published paper:

         Disorder-Enhanced Transport in Photonic Quasicrystals (Science 2011)

The third part of my thesis concentrates on transport in a fully disordered system where the spatial disorder also fluctuates randomly in time. In the experiments presented here, I studied the transport of waves in a paraxial optical system, which manifests analogies to the transport in a quantum system. I use the optical system as a model system to study transport through a temporally fluctuating spatial disorder, and demonstrated experimentally and numerically that an evolving random potential can give rise to hyper-transport: stochastic acceleration causing an initial wave-packet to expand at a rate faster than ballistic. I analyzed the hyper-transport phenomenon, and discussed its universal aspects which are relevant to all waves systems containing disorder.

My research on this area was summarized in the following published paper:

         Hyper-Transport of Light: Stochastic Acceleration by Virtue of Disorder (Nature Physics 2012)