Highly Directive Leaky-Wave Antennas Based on PT-Symmetric Metasurfaces

We present here parity-time (PT)-symmetric metasurfaces that effectively form an artificial channel (or metachannel) with exotic zero- or low-index characteristics. We show that this PT-synthetic metachannel locked at the coherent perfect absorber-laser (CPAL) point can support an almost nonattenuated fast-wave propagation, thus resulting in a highly directive radiation leakage. Further, the directive beam can be steered from broadside to end-fire by varying the gain-loss parameter (or non-Hermiticity) of the PT system.