Unidirectional invisibility of a PT-symmetric Bragg scatterer.
(A) The wave entering from the left does not recognize the existence of the periodic structure and goes through the sample entirely unaffected. On the contrary, a wave entering the same grating from the right experiences enhanced reflection. (B) Exact numerical evaluation [from Equation (1)] of transmission T and reflection R coefficients for a Bragg grating for n0=1, n1=10−3, L=12.5 π, and β=100. In case of a PT grating, the system is at the EP when n1=n2. In this case, RL is diminished (up to n1,22~10−6; see inset) for a broad frequency band, whereas RR is enhanced .