Fig. 1. Large-scale delay line array. (a) MRR-based binary tree 8×1 delay line^[33]; (b) MRR-based 4×4 delay line array^[38]; (c) 8×5 optical delay line phased array antenna based on ultra-low loss ultra-thin silicon waveguide^[21]; (d) 32×7 delay line arrays based on ultra-low-loss broadened silicon waveguides

Fig. 2. Large-scale optical switch array and large-scale delay line array. (a) Thermo-optical switches in 32×32 Benes topology ^[40]; (b) calibration-free 16×16 switch with Benes topology using low-phase error MZI^[41]; (c) 32×32 electro-optic switch with Benes topology^[44]; (d) 32 × 32 strictly-non-blocking optical switch^[47]; (e) 240×240 MEMS Crossbar silicon based large-scale array optical switch^[48]

Fig. 3. Programmable optically switched grid arrays^[52]. Feedback waveguide mesh networks based on (a) rectangular, (b) hexagonal, and (c) triangular topologies; (d) performance comparison of different feedback waveguide mesh structures

Fig. 4. Programmable optical neural network structure. (a) Schematic of two-layer 4×4 CNN experiment for speech recognition^[9]; (b) 8×8 optical signal processing circuits for multichannel optical switching^[20]; (c) schematic of the 8×8 CNN in implementing complex-valued networks and system workflow^[55]; (d) 16×16 programmable matrix computation processor; (e) 4096 computational metaphotonic accelerator^[56]; (f) 32-channel AWG-based optical reservoir calculations^[57]