Abstract
The backscattering mean free path , the average ballistic propagation length along a waveguide, quantifies the resistance of slow light against unwanted imperfections in the critical dimensions of the nanostructure. This figure of merit determines the crossover between acceptable slow-light transmission affected by minimal scattering losses and a strong backscattering-induced destructive interference when the waveguide length exceeds . Here, we calculate the backscattering mean free path for a topological photonic waveguide for a specific and determined amount of disorder and, equally relevant, for a fixed value of the group index which is the slowdown factor of the group velocity with respect to the speed of light in vacuum. These two figures of merit, and , should be taken into account when quantifying the robustness of topological and conventional (nontopological) slow-light transport at the nanoscale. Otherwise, any claim on a better performance of topological guided light over a conventional one is not justified.
- Received 31 July 2020
- Accepted 15 December 2020
DOI:https://doi.org/10.1103/PhysRevLett.126.027403
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