טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentNiv Avi
SubjectVectorial Vortices Obtained with Anisotropic Inhomogeneous
Subwavelength Structures
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Erez Hasman
Full Thesis textFull thesis text - English Version


Abstract

Optical vortices are analyzed according to their Pancharatnam-Berry phase and experimentally demonstrated using a geometric phase element consisting of space-variant subwavelength structures. First, the formation of spiral phase elements producing helical beams with different topological charges is treated. Second, a new class of vectorial vortices with space-variant axially symmetric polarization distributions that rotates upon propagation while maintaining a uniform Bessel intensity distribution is presented. Rotating intensity patterns are also demonstrated by transmitting vortices from this class through polarizer. Third, linearly polarized vectorial vortices are analyzed. It is shown that in the absence of a Pancharatnam phase, stable vectorial vortices that have no angular momentum arise. In contrast, if a Pancharatnam phase is present the vectorial vortices have orbital angular momentum and collapse upon propagation. Forth, the formation of vectorial, scalar and unpolarized polychromatic vortices is obtained by utilizing the unique properties of geometric Pancharatnam-Berry phase. Finally, spin-orbit interaction resulting from spatial polarization state manipulation is demonstrated. Unlike the usual dynamic spin-orbit interaction that splits degenerated states in their temporal frequency (energy) domain, this topological spin-orbit interaction splits states in their spatial frequencies (momentum) domain. To conclude, space-variant subwavelength structures were used for the formation of various geometric phase optical vortices, and their physical properties such as propagation and angular momentum were investigated. Advantage of these devices over conventional diffractive and refractive optical devices is discussed.