Topologically reconstructing Pancharatnam-Berry phase via encircling exceptional point for chiral spin-orbit interaction steering.

Photonic spin-orbit interaction (SOI) is related to Pancharatnam-Berry (PB) phase, which is usually imposed on the cross-polarized components of light incident on a metasurface in broadband manner. However, metasurfaces exhibiting exceptional points (EPs) can block the cross-polarization conversion channel, hinting at the possibility of EPs influencing SOI. Here, we demonstrate that the accumulation of PB phase is equivalent to the encircling of an EP, leading to topologically reconstructed PB phase. Through spin-Hall effect and spin-to-vortex conversion, we experimentally realize chiral SOI steering within chosen spectral ranges and polarization, showing suppression, inversion and doubling of the PB phase accumulated via rotation. Our work introduces the possibility to control SOIs via a topologically reconstructed PB phase, offering promising possibilities for applications such as information encryption.