Fig. 3: Numerical design of efficient topological coupler based on TSM principle. | Nature Communications

Fig. 3: Numerical design of efficient topological coupler based on TSM principle.

From: Efficient coupling of topological photonic crystal waveguides based on transverse spin matching mechanism

Fig. 3

a Schematic diagram of the designed coupler between the incident SWG and TWG waveguides. The optimized area has a compact footprint of 1.2 × 0.8 μm2 and is discretized into 12 × 8 pixels. Each pixel is occupied by either silicon or air according to the GA optimization. a1–a3 The distributions of the TS before optimization, after optimization (15 generations in GA), and the target distributions. b Changes of transmittance T and degree of TSM β with the number of iterations N in the GA optimizing process. The transmission increases from 52.8% to 96.3%, and β increases from 0.271 to 0.843 after 15 iterations of optimization. Inset: bandwidth of the coupler. c Electric field distributions of pre-optimization (N = 0) and after-optimization (N = 15) structures.

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