Abstract

Photonic-crystal waveguides formed at the interface between photonic topological insulators have recently received much attention as they promise robust forward propagation under a variety of disorder classes [1]. An example is time-reversal-symmetric valley-Hall (VH) topological waveguides, which can be implemented in dielectric slabs and free of intrinsic radiative losses. This makes them attractive as contenders for integrated optical waveguides to slow down light without suffering from backscattering at unavoidable fabrication defects [2]. While numerical simulations find VH interface waveguides to outperform conventional waveguides at the same group index for very small disorder levels [3], the failure of modelling real fabrication imperfections, i.e., surface roughness, due to the steep computational cost limits the scope of such results, warranting experimental investigation. We report here on the experimental characterization of the scattering properties of VH waveguides etched into a 220 nm-thick silicon membrane, an example of which is shown in Fig. 1a. Due to the glide symmetry of the waveguide and the degeneracy it enforces, the structure supports not only the topological mode ensured by the bulk-edge correspondence, but also a topologically trivial mode [4].

© 2023 IEEE