Direct observation of topological edge states in silicon photonic crystals: Spin, dispersion, and chiral routing

Nikhil Parappurath, Filippo Alpeggiani, L. Kuipers, Ewold Verhagen

Research output: Contribution to journalArticleScientificpeer-review

19 Citations (Scopus)
33 Downloads (Pure)

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' 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.

Original languageEnglish
Article numbereaaw4137
Number of pages9
JournalScience Advances
Volume6
Issue number10
DOIs
Publication statusPublished - 2020

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