Chiral modes in 2D PT-symmetric nanostructures

Abstract

We propose a 2-dimensonal PT-symmetric photonic honeycomb structure that supports chiral Block-likemodes being its excitation input and frequency dependent. We show that while the fundamental resonant frequency excites the counterclockwisemode, the clockwisemode is excited at the corresponding second harmonic frequency from the same input channel. The geometry is derived as the simplest nontrivial extension from 1-dimensional PT-symmetric systems to provide asymmetric coupling between harmonic wave components of the electromagnetic field. The PT-symmetric honeycomb is generated by a closed set of three lattice vectors that enable the simultaneous resonance of two disjoint triads of wavevectors in a circular coupling. As a basic effect, we numerically show the measurable asymmetric transmission of Gaussian light beams incident on such a finite-sized structure with a hexagonal shape, at the fundamental and second harmonic resonant frequencies.