Ultrastrong extraordinary transmission and reflection in PT-symmetric periodic triangle optical waveguide networks

We investigate the ultrastrong extraordinary transmission and reflection in the PT-symmetric periodic triangular optical waveguide network (PTSPTOWN). It is found that the extremum boundary points of photonic modes can be identified after reclassifying photonic modes. At the extremum boundary points of photonic modes, this network can generate ultrastrong extraordinary transmission and reflection, whose values can all arrive at the order of magnitude of 10^11 and are six orders of magnitude larger than that produced by aperiodic networks. We introduce the effective refractive index to explain the mechanism of generating extraordinary optical characteristics and find that the total gain and loss effect of this network defined by the imaginary part of the effective refractive index is exactly corresponding to the ultrastrong extraordinary transmission and reflection, but there is no clear correspondence between the group index of this network defined by the real part of the effective refractive index and the ultrastrong extraordinary transmission and reflection. It may deepen people's knowledge on PT-symmetric periodic optical waveguide networks and may be useful for the designing of extremely narrow filters, optical switches, high-efficient photon storage, and other all-optical devices.