טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentAlfassi Barak
SubjectOptics in Nonlocal Nonlinear Media and in Sub-Wavelength
Photonic Structures
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 two different parts:


- The first one deals with experimental and theoretical studies on solitons in highly-nonlocal nonlinear media. This includes: long range interactions between solitons, boundary force effects, and nonlocal surface-solitons.  

- The second part deals with wave propagation in optical waveguide arrays with sub-wavelength periodicity and sharp index contrasts.


The first part of my thesis concentrates on optical solitons. Solitons are self-localized wave packets arising from a robust balance between dispersion and nonlinearity which exhibit properties normally associated with particles. They have been discovered in a wide range of physical systems: from water waves, sound waves and charge-density waves to matter waves and electromagnetic waves (optical solitons). However, so far, the vast majority of experiments on solitons have been carried out in nonlinear media with a local response; that is, the nonlinear effect at a given location is a function of the electric field only at that same location. In contrast to ‘local nonlinearities’, the nonlinear response in non-local media is carried to regions beyond the range of localized wave packets. That is, the nonlinear effect at a given location is a function of the field at some non-locality range surrounding that location.

I use a highly non-local effect, arising from the thermal optical nonlinearity, to demonstrate some new features of solitons that have no counterpart in local nonlinear media. Nonetheless, the new concepts presented here are universal and can be implemented in other highly non-local nonlinear media.

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

?         Long range interactions between optical solitons [Nature Physics 2, 769 (2006)].

?         Boundary force effects exerted on solitons [Opt. Lett. 32,154 (2007)].

?         Nonlocal surface-wave solitons [Phys. Rev. Lett. 98, 213901 (2007)].

?         Incoherent surface solitons in effectively instantaneous nonlocal nonlinear media [Phys. Rev. A 80, 041808 (2009)].

In the second part of my thesis I studied wave propagation in waveguide array with sub-wavelength periodicity and sharp index contrasts. The dynamics in such optical nanostructure is generally fundamentally different from the dynamics in above-wavelength systems, leading to new phenomena such as briefings, lower-index guiding, optical forces on waveguides, and nonlinear effects such as optical control of light using resonant structures, and solitons arising from evanescent bands.