Research Fellows Directory
Dr Shuang Zhang
University of Birmingham
The optical properties are not only related to fundamental properties of the constituent materials down to the atomic and molecular levels, but also largely affected by the way how they are structured at a mesoscopic scale - much larger than atomic scale but much less than the wavelength of light. Metamaterials allow powerful control over electromagnetic waves, leading to phenomena that seems unnatural such as negative refraction and invisibility cloak.
Light propagation is not only controlled by the refractive index profile, but also by a physical effect called spin-orbit coupling. The spin of a tennis ball or football can induce a change in its trajectory when they traverse in air or when they bounce off a rough ground. This is the most intuitive picture of spin orbit (trajectory) interaction, which in the case of a tennis ball or football arises from the interaction between the surface of ball and air or the ground. Indeed, electrons and photons exhibit similar behaviour while the underlying mechanism of the spin-orbit coupling can be dramatically different. For photons, the spin represents one of the circular polarization states, and its interaction with orbit can happen at interfaces between two different media, leading to a transverse shift which, however, is so small that can hardly be detected. In this project, we aim to enhance this effect through structured surfaces – or metasurfaces and metamaterials, and to utilise this effect for investigating novel fundamental physics and for designing various practical applications. We have theoretically proposed that plasma under a strong magnetic field can serve as a new class of topological metamaterials in which the tailored spin orbit coupling leads to guiding of electromagnetic waves along its surfaces immune from scattering. In addition, we have introduced the concept of spin orbit coupling to nonlinear optics for achieving unprecedented control over the nonlinear harmonic generation processes.
Interests and expertise (Subject groups)