Non-Hermitian Topological Beam Splitting and Beam Encoding.

Non-Hermitian physics has attracted significant interest due to its exotic phenomena. However, non-Hermitian effects at topological interfaces and their potential applications remain largely unexplored. Here, based on an interface skin-effect model, we theoretically propose a non-Hermitian topological beam splitter (NHTBS) and experimentally demonstrate it as a proof of principle in a photonic spatiotemporal lattice using coupled fiber loops. By tuning the nonreciprocal parameters of the interface lattice, we demonstrate amplification of the wave packets at the output ports of the NHTBS and achieve fully tunable splitting ratios. Moreover, we carry out 4-bit temporal beam encoding using cascaded NHTBS units and also observe the amplification phenomenon. The output ports of the encoded beam exhibit high stability even in the presence of disorder perturbations on the asymmetric interactions. This work reveals the potential of non-Hermitian interface physics for enabling future multifunctional photonic information processors.