@article {Parappuratheaaw4137, author = {Parappurath, Nikhil and Alpeggiani, Filippo and Kuipers, L. and Verhagen, Ewold}, title = {Direct observation of topological edge states in silicon photonic crystals: Spin, dispersion, and chiral routing}, volume = {6}, number = {10}, elocation-id = {eaaw4137}, year = {2020}, doi = {10.1126/sciadv.aaw4137}, publisher = {American Association for the Advancement of Science}, abstract = {Topological protection in photonics offers new prospects for guiding and manipulating classical and quantum information. The mechanism of spin-orbit coupling promises the emergence of edge states that are helical, exhibiting unidirectional propagation that is topologically protected against back scattering. We directly observe the topological states of a photonic analog of electronic materials exhibiting the quantum spin Hall effect, living at the interface between two silicon photonic crystals with different topological order. Through the far-field radiation that is inherent to the states{\textquoteright} existence, we characterize their properties, including linear dispersion and low loss. We find that the edge state pseudospin is encoded in unique circular far-field polarization and linked to unidirectional propagation, thus revealing a signature of the underlying photonic spin-orbit coupling. We use this connection to selectively excite different edge states with polarized light and directly visualize their routing along sharp chiral waveguide junctions.}, URL = {https://advances.sciencemag.org/content/6/10/eaaw4137}, eprint = {https://advances.sciencemag.org/content/6/10/eaaw4137.full.pdf}, journal = {Science Advances} }