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Parity–time-symmetric whispering-gallery microcavities

Nature Physics volume 10, pages 394–398 (2014)Cite this article

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Abstract

Optical systems combining balanced loss and gain provide a unique platform to implement classical analogues of quantum systems described by non-Hermitian parity–time (PT)-symmetric Hamiltonians. Such systems can be used to create synthetic materials with properties that cannot be attained in materials having only loss or only gain. Here we report PT-symmetry breaking in coupled optical resonators. We observed non-reciprocity in the PT-symmetry-breaking phase due to strong field localization, which significantly enhances nonlinearity. In the linear regime, light transmission is reciprocal regardless of whether the symmetry is broken or unbroken. We show that in one direction there is a complete absence of resonance peaks whereas in the other direction the transmission is resonantly enhanced, a feature directly associated with the use of resonant structures. Our results could lead to a new generation of synthetic optical systems enabling on-chip manipulation and control of light propagation.

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Figure 1: PT-symmetric whispering-gallery-mode microcavities.
Figure 2: PT-symmetry breaking in coupled WGM microresonators.
Figure 3: Input–output relation in PT-symmetric WGMRs and reciprocity in the linear regime.
Figure 4: Experimentally observed unidirectional transmission for PT-symmetric WGM microresonators in the nonlinear regime.

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Acknowledgements

This work is supported by Army Research Office grant No. W911NF-12-1-0026. C.M.B. is supported by US Department of Energy grant No. DE-FG02-91ER40628. F.N. is partially supported by the RIKEN iTHES Project, MURI Center for Dynamic Magneto-Optics, Grant-in-Aid for Scientific Research (S), MEXT Kakenhi on Quantum Cybernetics and the JSPS through its FIRST program. F.L. and G.L.L. are supported by the National Natural Science Foundation of China (Grant Nos 11175094, 91221205), the National Basic Research Program of China (Grant No. 2011CB921602), and the Collaborative Innovation Center of Quantum Matter, Beijing, China.

Author information

Author notes

  1. Bo Peng and Şahin Kaya Özdemir: These authors contributed equally to this work.

Authors and Affiliations

  1. Department of Electrical and Systems Engineering, Washington University, St Louis, Missouri 63130, USA

    Bo Peng, Şahin Kaya Özdemir, Fuchuan Lei, Faraz Monifi & Lan Yang

  2. State Key Laboratory of Low-dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, China

    Fuchuan Lei & Gui Lu Long

  3. Department of Physics, Washington University, St Louis, Missouri 63130, USA

    Mariagiovanna Gianfreda & Carl M. Bender

  4. Dipartimento di Matematica e Fisica Ennio De Giorgi, Universita del Salento and I.N.F.N. Sezione di Lecce, Via Arnesano I-73100 Lecce, Italy,

    Mariagiovanna Gianfreda

  5. Tsinghua National Laboratory for Information Science and Technology, Beijing 100084, China

    Gui Lu Long

  6. Department of Electrical Engineering, Stanford University, Stanford, California 94305, USA

    Shanhui Fan

  7. Center for Emergent Matter Science, RIKEN, Saitama 351-0198, Japan

    Franco Nori

  8. Physics Department, University of Michigan, Ann Arbor Michigan 48109-1040, USA

    Franco Nori

Authors
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Contributions

S.K.O. and L.Y. conceived the idea and designed the experiments; B.P. performed the experiments with help from F.L., F.M. and S.K.O. Theoretical background and simulations were provided by F.L., F.M., M.G., C.M.B., S.F. and F.N. All authors discussed the results, and S.K.O. and L.Y. wrote the manuscript with inputs from all authors. L.Y. supervised the project.

Corresponding authors

Correspondence to Şahin Kaya Özdemir or Lan Yang.

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The authors declare no competing financial interests.

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Peng, B., Özdemir, Ş., Lei, F. et al. Parity–time-symmetric whispering-gallery microcavities. Nature Phys 10, 394–398 (2014). https://doi.org/10.1038/nphys2927

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