Exceptional Points in Flat Optics: A Non-Hermitian Line-Wave Scenario

Line waves are recently discovered wave entities that localized along two directions, and therefore can be viewed as the one-dimensional counterpart of surface waves. These supported at discontinuities reactance and/or resistance low-dimensional materials such metasurfaces or graphene. Here, a broader class non-Hermitian surface-impedance junctions is studied support coupled line waves, allows investigating different waveguiding mechanisms in unified framework. It theoretically demonstrated that, under parity-time-symmetry conditions, exceptional points occur truly flat-optics scenario, hence endowing these systems with attractive features both line-wave exceptional-point physics, shedding further light on phase transitions existing systems. also shown required parameters compatible those attainable typical models photoexcited graphene terahertz frequencies. Besides providing additional understanding physics which still its infancy, results pave way to intriguing developments largely unexplored field flat optics, possible applications ranging from sensing lasing on-chip optical signal processing.