Time reversal and holography with spacetime transformations

By Vincent Bacot, M. Labousse, A. Eddi, Mathias Fink, Emmanuel Fort. Nature Physics, 2015

289 citations recorded by the source corpus.

Wave control is usually performed by spatially engineering the properties of a medium. Because time and space play similar roles in wave propagation, manipulating time boundaries provides a complementary approach. Here, we experimentally demonstrate the relevance of this concept by introducing instantaneous time mirrors. We show with water waves that a sudden change of the effective gravity generates time-reversed waves that refocus at the source. We generalize this concept for all kinds of waves, introducing a universal framework which explains the effect of any time disruption on wave propagation. We show that sudden changes of the medium properties generate instant wave sources that emerge instantaneously from the entire space at the time disruption. The time-reversed waves originate from these ‘Cauchy sources’, which are the counterpart of Huygens virtual sources on a time boundary. It allows us to revisit the holographic method and introduce a new approach for wave control. Using a water bath subject to a sudden vertical jolt — representing a change in the effective gravity — researchers demonstrate the concept of a ‘time mirror’, where time-reversed waves return to their point source following a downward jolt.

Subfields: Biomedical Engineering, Electronic, Optical and Magnetic Materials, Oceanography

View Paper: https://www.semanticscholar.org/paper/4e691bda8498b0cebe2edb89dd813781574f0bac

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In Biomedical Engineering

In Electronic, Optical and Magnetic Materials

Citations in the corpus

Spacetime Metamaterials—Part II: Theory and Applications (2020, methodology): “focusing may be considered as a spacetime generalization of the pure-time time-reversal focusing [18].”
Photonics of time-varying media (2021, background): “Until now, the experimental work demonstrating time-reversal at a temporal interface has been limited to water-wave phenomena by Fink’s group, whereby a water tank was uniformly shaken by an impulse, leading to the refocusing of the waves back to their emission point.(52) In addition to limitations ”
Spatiotemporal light control with active metasurfaces (2019, background): “Time reversal and negative refraction (NR) are interrelated optical processes (100, 105), which are achievable by using time-dependent optical materials (101) or a four-wave mixing (FWM) optical nonlinear process (106).”
Memory formation in matter (2018, background): “Remarkably, recent experiments have shown that this reversal of dynamics may be achieved in real time (Bacot et al., 2016).”