Direct observation of topological edge states in silicon photonic crystals (Conference Presentation)

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

doi:10.1117/12.2529236

9 September 2019 Direct observation of topological edge states in silicon photonic crystals (Conference Presentation)

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

Proceedings Volume 11081, Active Photonic Platforms XI; 110811L (2019) https://doi.org/10.1117/12.2529236
Event: SPIE Nanoscience + Engineering, 2019, San Diego, California, United States

Abstract

Leveraging topological protection in the photonic domain could lead to new ways to transport information on-chip, potentially increasing its robustness to scattering at disorder. We realize a photonic analogue of topological insulators based on the quantum spin Hall effect in symmetry-broken photonic crystals. We directly observe the propagation of topological edge states at telecom wavelengths in a silicon-on-insulator platform. Analyzing their properties through their far-field radiation allows characterizing their inherent spin, dispersion, and propagation. We reveal that the radiation of the topological states carries a signature of their origin in photonic spin-orbit coupling, linking the unidirectional propagation of two states with opposite pseudospin to circular far-field polarization. Polarimetric Fourier spectroscopy allows mapping the edge state dispersion and characterize their quality factors. The positive and negative group velocity modes can be selectively excited with circular polarization of opposite handedness. Moreover, we detect a small gap at the edge state crossing that is related to spin-spin scattering, inherent to the symmetry breaking at the edge, and a defining difference between photonic and electronic topological insulators. We image edge state propagation in real-space microscopy, and show how they can be routed at sharp waveguide junctions, attesting to their topologically protected nature. Thus, we observe the unique nature of topologically protected light transport in photonic crystals, through a technique that holds great promise for developing novel topological systems for various applications, including integrated photonic components, quantum optical interfaces, and nanoscale lasing.

Conference Presentation

Citation Download Citation

Nikhil Parappurath, Filippo Alpeggiani, L. Kuipers, and Ewold Verhagen "Direct observation of topological edge states in silicon photonic crystals (Conference Presentation)", Proc. SPIE 11081, Active Photonic Platforms XI, 110811L (9 September 2019); https://doi.org/10.1117/12.2529236

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KEYWORDS

Photonic crystals

Crystals

Silicon photonics

Wave propagation

Dielectrics

Dispersion

Polarization

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