Quantifying the Robustness of Topological Slow Light

• Published in: Physical review letters 2021-01, Vol.126 (2), p.027403-027403, Article 027403
• Main Authors: Arregui, Guillermo, Gomis-Bresco, Jordi, Sotomayor-Torres, Clivia M, Garcia, Pedro David
• Format: Article
• Language: English
• Subjects: Backscattering; Crossovers; Figure of merit; Group velocity; Light; Light speed; Light transmission; Mean free path; Robustness; Topology; Wave propagation; Waveguides
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.126.027403

The backscattering mean free path ξ, 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 L exceeds ξ. 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 n_{g} which is the slowdown factor of the group velocity with respect to the speed of light in vacuum. These two figures of merit, ξ and n_{g}, 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.