Optical properties of a designed passive unidirectional reflectionless DL-LRSPP PT-symmetric grating structure.
(A) 3D view of a DL-LRSPP PT-symmetric grating structure. (B) Real and imaginary parts of effective index near the nR crossing region of the ssb0 (fundamental) and sab3 (asymmetric high-order) modes. Vertical red dashed lines indicate four widths selected for a PT-symmetric grating. (C) Schematic of the real and imaginary index distribution within one period. (D) Reflectance from the left side Rl and the right side Rr of a passive PT-symmetric grating operating at the EP .