Nonreciprocal optical Bloch-Zener oscillations in ternary parity-time-symmetric waveguide lattices

We demonstrate a kind of ternary parity-time (PT)-symmetric complex waveguide arrays to observe nonreciprocal optical Bloch-Zener oscillations (OBZOs) at the PT thresholds. The waveguide arrays are periodically constructed with a unit of a dielectric waveguide sandwiched by a loss and a gain waveguides. The nonreciprocal optical Bloch-Zener oscillations are attributed to the unidirectional Bragg scattering behaviors of light in the systems, which can be controlled by the propagation constant mismatch between dielectric waveguides and loss or gain waveguides through independently tuning the propagation constants of the dielectric waveguides of the units.