טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentShitrit Nir
SubjectSpinoptics: Optical Spin Symmetry Breaking in Plasmonic
Nanostructures
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Erez Hasman


Abstract

Surface plasmons are electromagnetic excitations propagating at the interface between a dielectric and a conductor, evanescently confined in the perpendicular direction. By altering the structure of a metal’s surface, the properties of surface plasmons, in particular their interaction with light, can be tailored, which offers the potential for developing new types of photonic devices with length scales that are much smaller than those currently achieved.

A wide spectrum of plasmonic nanostructures has been studied recently due to their physical and technological impact. Plasmonic systems have been shown to be resonantly excited when the linear momentum selection rule is fulfilled. However, conservation of total angular momentum in a closed physical system results in additional selection rules related to angular momentum (AM). The AM of an optical beam comprises the intrinsic component, the spin, associated with the handedness of the circular polarization, and the extrinsic component, orbital AM (OAM), associated with a spiral phase front. Here, we demonstrate a plasmonic nanostructure which exhibits a crucial role of an AM selection rule in a light-surface plasmon scattering process. In our experiment, the intrinsic AM of the incident radiation is coupled to the extrinsic momentum of the surface plasmons via spin-orbit interaction, which is manifested by a geometric Berry phase. Due to this effect, we achieved a symmetry breaking resulting in a spin-dependent enhanced transmission through coaxial nanoapertures even in rotationally symmetric structures. We believe that spin-based plasmonic effects provide additional physical insight into the phenomenon of extraordinary light transmission and inspire one for a new type of spinoptics nanodevices.