Theoretical seminar | 25 September 2024

Spin and orbital angular momenta are fundamental properties of light that have garnered significant attention in recent decades. In the past ten years, transverse spin has been demonstrated in various physical systems. However, transverse spin angular momentum (t-SAM) and its characteristics remain a relatively unexplored research area.

Transverse spin angular momentum (t-SAM) refers to a spin vector perpendicular to the direction of light propagation, which naturally occurs in tightly confined electromagnetic waves. However, the far-field generation of t-SAM at the maximum intensity point of focused light has not been achieved. In this study, we use an asymmetric metasurface with complete phase and polarization control to bridge this gap and generate an electromagnetic field that supports t-SAM at a focal point.
Our theoretical and experimental results demonstrate that the transverse spin distribution in a focused light beam can be controlled by the specifically created metasurface. For the first time, we have designed and experimentally tested a metadevice capable of producing significant transverse spin at its focus.
We numerically confirm that the proposed metalens can add torque functionality to optical tweezer devices while still producing enough optical trapping force. Other potential applications of the proposed innovative approach include quantum optics, nanometrology, and directional scattering.