From the time-reversal mirror to the instantaneous time mirror

Abstract

Because time and space play a similar role in wave propagation, wave control can be obtained by manipulating spatial boundaries or by manipulating time boundaries. These two dual approaches will be discussed in this paper in the context of the generation of time-reversed waves. The first approach uses the “time-reversal mirror” approach with wave manipulation along a spatial boundary sampled by a finite number of antennas. In the second approach, waves are manipulated from a time boundary and we show that “instantaneous time mirrors”, simultaneously acting in the entire space can also radiate time-reversed waves.