Scalable Photonic Crystal Waveguides With 2 dB Component Loss

Minimizing the insertion loss of individual components is of paramount importance for large-scale photonic integrated circuits. The measured component insertion losses (5-20 dB) of photonic crystal waveguides devices are well beyond numerical predictions (< 0.1 dB). The additional loss is the sum of the coupling loss and propagation loss in photonic crystal waveguides. Mode mismatch and deformation in suspended structures increase the coupling loss. Nanofabrication-related geometric inhomogeneity increases the propagation loss. The fabrication variation and offsets of periodic or gradient nanophotonic structures are foundry dependent and need to be calibrated for each processing line. In this work, we demonstrate the first low loss photonic crystal waveguides through AIM photonics multi-project-wafer run. For sub-millimeter-long photonic crystal waveguides, 2 dB total component loss and 40 dB extinction ratio are observed across dies. A three-dimensional coupler between the channel and photonic crystal waveguides reduces the insertion loss to less than 1 dB per port. The high extinction ratio is attributed to the excellent geometric homogeneity of the nano-manufactured nanophotonic structures.