Ultralow Loss Coupling Tuning of Photonic Accelerators

By leveraging the high propagation speed and inherent parallelism of light, hardware accelerators based on photonic integrated circuits enable high‐speed, low‐power computing, positioning them as promising solutions to meet the rapidly increasing computational demands driven by advancements in artificial intelligence (AI). Within photonic accelerators directional couplers are crucial components for splitting and combining light, facilitating parallel computation and addition operations. However, fabrication imperfections frequently cause deviations in the coupling ratio from its intended value, significantly impairing accelerator performance. This study demonstrates a scalable and nonvolatile approach to flexibly adjust the coupling ratio of fabricated directional couplers by strategically placing polymer patches around their waveguides. This method introduces exceptionally low insertion loss of ≈0.01 dB and can effectively adapt directional couplers with varying initial coupling ratios. This method is applied to a photonic crossbar array, substantially reducing the fabrication‐induced power discrepancy among output ports from 389% to just 8%. This approach presents an innovative strategy for efficiently compensating fabrication errors in integrated photonic circuits.