Topology-Optimized Interference-Based Compact Photonic Logic Units

Interference is a fundamental yet crucial phenomenon in photonics, enabling precise control over light’s phase, amplitude, and intensity. This principle has enabled significant improvements in various application areas, such as signal processing, spectroscopy, optical computing, and data communication. Leveraging this principle, we introduce compact, topology-optimized, inverse-designed devices that advance the scalability and efficiency of photonic computing systems. Two devices are demonstrated: a logic gate performing basic AND and OR operations and a 1-bit optical magnitude comparator. By integrating these devices, our design simplifies circuit complexity, reduces the footprint, and lowers energy consumption in photonic circuits. Both devices are highly compact, with dimensions of 5 × 6 μm², and fabricated on a silicon-on-insulator (SOI) platform using e-beam lithography. Experimental results conducted at around 1550 nm closely match simulations, with the AND gate achieving a contrast ratio of 5.22 dB and the OR gate demonstrating transmission values as high as −0.88 dB, confirming their high efficiency, high bandwidth, and reliability. These findings highlight the transformative potential of interference-based, inverse-designed linear photonic devices in enabling highly integrated, robust, and energy-efficient on-chip optical computing systems for networks, processors, and programmable photonics.