Anti-parity-time symmetry enabled on-chip chiral polarizer

Encircling an exceptional point (EP) in a parity-time (PT) symmetric system has shown great potential for chiral optical devices, such as chiral mode switching for symmetric and antisymmetric modes. However, to our best knowledge, chiral switching for polarization states has never been reported, although chiral polarization manipulation has significant applications in imaging, sensing, communication, etc. Here, inspired by the anti-PT symmetry, we demonstrate, for the first time to our best knowledge, an on-chip chiral polarizer by constructing a polarization-coupled anti-PT symmetric system. The transmission axes of the chiral polarizer are different for forward and backward propagation. A polarization extinction ratio of over 10 dB is achieved for both propagating directions. Moreover, a telecommunication experiment is performed to demonstrate the potential applications in polarization encoding signals. It provides a novel functionality for encircling-an-EP parametric evolution and offers a new approach for on-chip chiral polarization manipulation.