Imaging topological edge states in silicon photonics


Topological features—global properties not discernible locally—emerge in systems ranging from liquid crystals to magnets to fractional quantum Hall systems. A deeper understanding of the role of topology in physics has led to a new class of matter—topologically ordered systems. The best known examples are quantum Hall effects, where insensitivity to local properties manifests itself as conductance through edge states that is insensitive to defects and disorder. Current research into engineering topological order primarily focuses on analogies to quantum Hall systems, where the required magnetic field is synthesized in non-magnetic systems. Here, we realize synthetic magnetic fields for photons at room temperature, using linear silicon photonics. We observe, for the first time, topological edge states of light in a two-dimensional system and show their robustness against intrinsic and introduced disorder. Our experiment demonstrates the feasibility of using photonics to realize topological order in both non-interacting and many-body regimes.

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Figure 1: Experimental set-up.
Figure 2: Edge states around a magnetic domain.
Figure 3: Edge state propagation in a homogeneous magnetic field (8 × 8 array).
Figure 4: Edge state protection against a defect.


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The authors thank J. Chen, K. Srinivasan, M. Lukin, A. Melloni, M. Fournier, G. Solomon and E. Waks for stimulating discussions and experimental help. M.H. thanks the Institute for Quantum Optics and Quantum Information (Innsbruck) for hospitality. This research was supported by a US Army Research Office Multidisciplinary University Research Initiative award (W911NF0910406) and the National Science Foundation through the Physics Frontier Center at the Joint Quantum Institute. Disclaimer: Certain commercial equipment, instruments or materials are identified in this paper to foster understanding. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the materials or equipment are necessarily the best available for the purpose.

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M.H. conceived the experiment. M.H., J.F., A.M. and J.M.T. designed the chips. M.H., S.M. and J.F. carried out the experiment and analysed the data. M.H. and J.M.T. wrote the manuscript. All authors contributed considerably.

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Correspondence to M. Hafezi.

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The authors declare no competing financial interests.

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Hafezi, M., Mittal, S., Fan, J. et al. Imaging topological edge states in silicon photonics. Nature Photon 7, 1001–1005 (2013).

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