Hybrid silicon photonic switching enabled by Non-Hermiticity

Non-Hermitian photonics, by harnessing the full spectrum of complex dielectric permittivity, fundamentally transforms wave propagation through complex optical potentials, sparking a broad range of new photonic applications. Through the delicate gain-loss interplay of parity-time symmetry and its breaking, interactions between even two entities become counter-intuitive and captivating. Here, we achieve the first scalable non-Hermitian switching network using hybrid III-V/Si integration on a two-layer photonic chip. This hybrid platform combines a silicon bottom layer and a top InGaAsP layer that provides optical gain or loss. By tuning the gain level in the top layer, vertically coupled waveguides can operate below or above the exceptional point, facilitating light switching across two layers and multiple input-output ports. For a single switching unit, the dynamic is ultrafast, within hundreds of picoseconds. In a large-scale network, this setup supports non-blocking configurations and diverse connectivity. Our approach adds scalable non-Hermitian switching to the photonic design toolkits to simultaneously boost the switching time and bandwidth density to cutting-edge levels, therefore paving the way for compact and ultrafast monolithic integrated silicon photonics in next-generation optical information networks.