טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentSchley Ran
SubjectLoss-Proof Self-Accelerating Beams
DepartmentDepartment of Physics
Supervisor ? 18? Mordechai Segev
Full Thesis textFull thesis text - English Version


Abstract

My M.Sc. research focuses on a theoretical and experimental study of self-accelerating optical beams. The term self-accelerating beams refers to a wide class of optical beams which maintain their intensity pattern along a curved trajectory, and share several interesting features such as diffractionless propagation, transverse acceleration and self-healing. In recent years, a plethora of applications have been demonstrated for accelerating beams, from particle micromanipulation on curved trajectories and curved light-induced plasma channels to self-bending plasmons, laser machining of curved structures, and even self-bending electron beams.

Most of the applications of accelerating beams involve the interaction of light with matter, hence their propagation range is limited by absorption and scattering. In my work, I study the question of propagation of accelerating beams inside lossy media (absorbing or scattering), and show that accelerating beams feature a novel self-healing mechanism that allows loss-proof solutions - beams that propagate without attenuation of the intensity structure of their main lobes inside lossy media. I utilize this new kind of self-healing property of the accelerating beam to overcome linear and nonlinear losses, and introduce loss-proof accelerating beams. These beams, as analytic solutions of the full Maxwell equations with losses, propagate in absorbing media while maintaining their peak intensity in spite of the loss. While the power such beams carry does decay during propagation, the intensity structure of their main lobe region is maintained over large propagation distances. Such beams can be used to create long-range loss-proof plasmons and manipulate particles in absorbing or scattering fluids, steering the particles to steep angles. In transparent media (e.g., free space), these beams show exponential growth in intensity during propagation, which facilitates other novel applications in particle acceleration and ignition of nonlinear processes. Additionally, I find nonlinear loss-proof solutions that can overcome nonlinear losses such as two-photon absorption, and suggest a general formulation that allows loss-proof solutions for other nonlinearities, such as Kerr, quadratic or nonlocal.

In the experimental part of my research, I demonstrate optical micromanipulation of particles using non-paraxial accelerating beams (both ordinary and loss-proof), to achieve acceleration of particles along much steeper curved trajectories than ever achieved. These beams accelerate particles at curved trajectories up to 40°-50°, as opposed to former paraxial experiments, that have demonstrated limited paraxial bending in small angles. Such beams could be of great use to the optofluidic community, where precise optical control of microparticles in a fluid is a highly desirable object.