Chiral modes and directional lasing at exceptional points

@article{Peng2016ChiralMA,
  title={Chiral modes and directional lasing at exceptional points},
  author={Bo Peng and Şahin Kaya {\"O}zdemir and Matthias Liertzer and Weijian Chen and Johannes Kramer and Huzeyfe Yılmaz and Jan Wiersig and Stefan Rotter and Lan Yang},
  journal={Proceedings of the National Academy of Sciences},
  year={2016},
  volume={113},
  pages={6845 - 6850}
}
Significance Exceptional points (EPs) emerge when a system with loss or gain is tuned such that its eigenvalues and the corresponding eigenstates coalesce. By operating close to two EPs, we achieved a dynamic control of the rotation direction of light in a whispering-gallery-mode (WGM) resonator. This enabled us to tune the emission direction of a WGM microlaser from bidirectional, when the system is away from the EPs, to unidirectional emission at EPs and to reverse the emission direction by… 
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