Exceptional point protected robust on‐chip optical logic gates

Optical logic gates are crucial components for information processing and communication using photons. Current optical logic gates typically rely on the light interference principle which requires an accurate manipulation of the dynamical phase of light, making the device quite sensitive to system disturbances such as fabrication errors. Here we introduce non‐Hermitian principles into the design of optical logic gates that work in the signal transmission process. We propose an exclusive‐or gate for silicon‐on‐insulator platform by employing the physics in the exceptional point (EP) encirclement process. The EP induced mode switching behavior is applied to manipulate the phase of light which is topologically protected by the energy surface around the EP. As a result, the performance of the device is found to be extremely robust to structural parameter disturbances. The proposed non‐Hermitian principle is expected to find applications for other on‐chip photonic devices toward high robust performance.