Absorbing Exceptional Point of Coherent Vortex Beams

Coherent perfect absorption at exceptional point (CPA-EP) is of great interest in wave systems for its unique absorption behavior. However, most CPA-EPs achieved so far are confined to plane-wave systems, limiting their versatility. Here, we realize CPA-EPs in chiral spaces via topological vortex beams, using metamaterials with tailored symmetry. We show that chiral CPA-EPs arise from the delicate interplay of mode channels encoding different topological charges (TCs), and TC channels supported by orbital angular momentum significantly boost the channel capacity of CPA-EPs. Notably, through rotational operations, the chiral system enables dynamic switching of absorption capacity and state transformation of CPA-EPs, in which the introduced geometric phase provides a crucial route for enhancing sensitivity via lower-order EPs. Crucially, we further demonstrate the unique coexistence of sensitivity (in EP state) and robustness (in CPA state) within the chiral space. Our findings broaden CPA-EP research and enable advanced devices on chiral wave systems.