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Non-Hermitian photonics based on parity–time symmetry

Abstract

Nearly one century after the birth of quantum mechanics, parity–time symmetry is revolutionizing and extending quantum theories to include a unique family of non-Hermitian Hamiltonians. While conceptually striking, experimental demonstration of parity–time symmetry remains unexplored in quantum electronic systems. The flexibility of photonics allows for creating and superposing non-Hermitian eigenstates with ease using optical gain and loss, which makes it an ideal platform to explore various non-Hermitian quantum symmetry paradigms for novel device functionalities. Such explorations that employ classical photonic platforms not only deepen our understanding of fundamental quantum physics but also facilitate technological breakthroughs for photonic applications. Research into non-Hermitian photonics therefore advances and benefits both fields simultaneously.

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Fig. 1: PT symmetry and phase transition in photonics.
Fig. 2: Experimental demonstrations of PT symmetry in different photonic platforms.
Fig. 3: Novel optical effects enabled by PT symmetry.
Fig. 4: CPA laser concept and realization.
Fig. 5: Unidirectional reflectionless resonance.
Fig. 6: Orbital angular momentum microlaser by unidirectional laser actions.

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Acknowledgements

L.F. acknowledges support from the Army Research Office (W911NF-15-1-0152), the Army Research Office Young Investigator Research Program (W911NF-16-1-0403) and the National Science Foundation (DMR-1506884 and ECCS-1507312). R.E. acknowledges support from the National Science Foundation (ECCS-1545804). L.G. acknowledges support from the National Science Foundation (DMR-1506987).

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L.F. led the project. All authors contributed significantly to the preparation of the manuscript.

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Correspondence to Liang Feng or Li Ge.

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Feng, L., El-Ganainy, R. & Ge, L. Non-Hermitian photonics based on parity–time symmetry. Nature Photon 11, 752–762 (2017). https://doi.org/10.1038/s41566-017-0031-1

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