Optical diode based on the one-way light-speed anisotropy
  We report that a triangular Fabry-Perot resonator filled with a parity-odd linear anisotropic medium exhibiting the one-way light speed anisotropy acts as a perfect diode. A Linear crystal such as the nematic liquid crystals whose molecular structures break parity can exhibit the one-way light speed anisotropy. The one-way light speed anisotropy also can be induced in a non-linear medium in the presence of constant electric and magnetic field strengths. 
Qasem Exirifard
physics.optics