Chiral modes and directional lasing at exceptional points

Bo Peng, Şahin Kaya Özdemir, Matthias Liertzer, Weijian Chen, Johannes Kramer, Huzeyfe Yilmaz, Jan Wiersig, Stefan Rotter, Lan Yang

Research output: Contribution to journalArticlepeer-review

437 Scopus citations


Controlling the emission and the flow of light in micro- and nanostructures is crucial for on-chip information processing. Here we show how to impose a strong chirality and a switchable direction of light propagation in an optical system by steering it to an exceptional point (EP) - a degeneracy universally occurring in all open physical systems when two eigenvalues and the corresponding eigenstates coalesce. In our experiments with a fiber-coupled whispering-gallery-mode (WGM) resonator, we dynamically control the chirality of resonator modes and the emission direction of a WGM microlaser in the vicinity of an EP: Away from the EPs, the resonator modes are nonchiral and laser emission is bidirectional. As the system approaches an EP, the modes become chiral and allow unidirectional emission such that by transiting from one EP to another one the direction of emission can be completely reversed. Our results exemplify a very counterintuitive feature of non-Hermitian physics that paves the way to chiral photonics on a chip.

Original languageEnglish (US)
Pages (from-to)6845-6850
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number25
StatePublished - Jun 21 2016

All Science Journal Classification (ASJC) codes

  • General


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