Quantifying the Robustness of Topological Slow Light

Low-dimensional nanostructured materials can guide light propagating with very low group velocity vg. However, this slow is significantly sensitive to unwanted imperfections in the critical dimensions of nanostructure. The backscattering mean free path, xi, average ballistic propagation length along waveguide, quantifies robustness against type structural disorder. This figure merit determines crossover between acceptable slow-light transmission affected by minimal scattering losses and a strong backscattering-induced destructive interference when xi exceeds waveguide L. Here, we calculate path for topological photonic specific determined amount disorder and, equally relevant, fixed value index ng which slowdown factor respect speed vacuum. These two figures merit, ng, should be taken into account quantifying conventional (non-topological) transport at nanoscale. Otherwise, any claim on better performance guided over one not justified.