The first generation G(1) of the SG has nine blue sites. G(n) has three copies of G(n−1), sharing three corner sites. The fractal lattice of helical waveguides is generation G(4) with a total of 204 sites. Each blue site marks the position of a helical waveguide. The helicity of the waveguides introduces an artificial vector potential Az=A0sinΩz,−cosΩz,0. For presentation simplicity, we draw only the three-dimensional schematic of a G(1) lattice of helical waveguides
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