Optical fractal and exceptional points in PT symmetry Thue-Morse photonic multilayers

Abstract

The non-Hermiticity is explored in parity-time–symmetric (PT–symmetric) dielectric multilayers abiding by Thue-Morse (T-M) sequence. The T-M sequence is aperiodic and an optical fractal phenomenon in transmission spectra arises as the sequence number increases, while in the space of reflection spectrum, exceptional points (EPs) are induced. By increasing the gain-loss factor of dielectrics, EPs split and then degenerate. The splitting EPs disturb the optical fractal states slightly, which approves asymmetric localization of electric fields. Furthermore, there are four ±π/2 jump points in the curve of forward and backward reflection coefficients phase (φrf+φrb)/2. The study paves a way towards the applications for wavelength sensors and phase modulators.