Non-Decaying Leaky Surface Waves

A Sinusoidally Modulated Reactive Sheet (SMRS) can be designed to support TE or TM surface wave propagation with at least one spatial harmonic within the light cone. Due to radiative losses associated with the spatial harmonics within the light cone, the wavenumber of the fundamental surface wave is complex. In this work, we compensate the loss associated with the leakage by coupling the SMRS to an active impedance sheet. Solving the dispersion relation for the coupled configuration shows that at a particular modulation depth, the wavenumber associated with the dominant surface wave is purely real despite the radiative losses. Although an exceptional point has not been observed, the structure is reminiscent of the balanced gain and loss configuration of coupled waveguides exhibiting parity-time symmetry except here the loss is due to leaky wave radiation.