Chiral modes and directional lasing at exceptional points

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…

• DF
  Deutsche Forschungsgemeinschaft

  Award: WI1986/6-1
• AS
  Austrian Science Fund

  Award: SFB-NextLite F49-P10
• AR
  Army Research Office

  Award: W911NF-12-1-0026