Breakdown of Spin-to-Helicity Locking at the Nanoscale in Topological Photonic Crystal Edge States

S. Arora, T. Bauer, N. Parappurath, R. Barczyk, E. Verhagen, L. Kuipers*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

5 Citations (Scopus)
39 Downloads (Pure)

Abstract

We measure the local near-field spin in topological edge state waveguides that emulate the quantum spin Hall effect. We reveal a highly structured spin density distribution that is not linked to a unique pseudospin value. From experimental near-field real-space maps and numerical calculations, we confirm that this local structure is essential in understanding the properties of optical edge states and light-matter interactions. The global spin is reduced by a factor of 30 in the near field and, for certain frequencies, flipped compared to the pseudospin measured in the far field. We experimentally reveal the influence of higher-order Bloch harmonics in spin inhomogeneity, leading to a breakdown in the coupling between local helicity and global spin.

Original languageEnglish
Article number203903
Number of pages6
JournalPhysical Review Letters
Volume128
Issue number20
DOIs
Publication statusPublished - 2022

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