Efficient Phase Conjugation in a Space-Time Leaky Waveguide

Temporal interfaces, arising when the electromagnetic properties of a medium are abruptly switched in time, have been recently raising interest as the dual of spatial interfaces. Their study has been mostly focused on switching in time the properties of infinite media, for which the wave momentum is conserved, yielding the dual phenomenon of spatial interfaces at which the frequency is conserved. Here, we demonstrate interesting phenomena arising at temporal interfaces when they involve finite-size resonant structures. By abruptly changing the permittivity of a grounded dielectric slab supporting a strong leaky-wave resonance, we show the possibility of achieving efficient phase conjugation of the stored electromagnetic energy with a pair of suitably tailored switching events. Our work opens interesting opportunities for space-time metamaterials in the context of imaging, holography, and efficient frequency conversion.