Observation of backscattering-immune chiral electromagnetic modes   without time reversal breaking
  A strategy is proposed to realize robust transport in time reversal invariant photonic system. Using numerical simulation and microwave experiment, we demonstrate that a chiral guided mode in the channel of a three-dimensional dielectric woodpile photonic crystal is immune to the scattering of a square patch of metal or dielectric inserted to block the channel. The chirality based robust transport can be realized in nonmagnetic dielectric materials without any external field. 
Wen-Jie Chen, Jian-Wen Dong, Zhi Hong Hang, Xiao Xiao, He-Zhou Wang,   and C. T. Chan
physics.optics