Electrical tunability due to coalescence of exceptional points in   parity-time symmetric waveguides
  We demonstrate theoretically the electric tunability due to coalescence of exceptional points in PT-symmetric waveguides bounded by imperfect conductive layers. Owing to the competition effect of multimode interaction, multiple exceptional points and PT phase transitions could be attained in such a simple system and their occurrences are strongly dependent on the boundary conductive layers. When the conductive layers become very thin, it is found that the oblique transmittance and reflectance of the same system can be tuned between zero and one by a small change in carrier density. The results may provide an effective method for fast tuning and modulation of optical signals through electrical gating. 
Jin Wang, Hui Yuan Dong, Raymond P. H. Wu, T. C. Mok and Kin Hung Fung
physics.optics