Pulse dynamics of flexural waves in transformed plates

Kun Tang (1) , Chenni Xu (2, 1) , Sebastien Guenneau (3) , Patrick Sebbah (1)

1 The Jack and Pearl Resnick Institute for Advanced Technology
2 Department of Physics, Zhejiang University
3 Abraham de Moivre

Coordinate-transformation-inspired optical devices have been mostly examined in the continuous-wave regime: the performance of an invisibility cloak, which has been demonstrated for monochromatic excitation, would inevitably deteriorate for short pulses. Here we investigate pulse dynamics of flexural waves propagating in transformed plates. We propose a practical realization of a waveshifter and a rotator for flexural waves based on the coordinate transformation method. Time-resolved measurements reveal how our waveshifter deviates a short pulse from its initial trajectory, with no reflection at the bend and no spatial and temporal distortion of the pulse. An invisible cloak for flexural waves is proposed based on this elementary transformed device. Extending our strategy to cylindrical coordinates, we design a perfectly invisible wave rotator. We demonstrate experimentally how a pulsed plane wave is twisted inside the rotator, while its wavefront is recovered behind the rotator and the pulse shape is preserved, with no extra time delay. We propose the realization of the dynamical mirage effect, where an obstacle is seen to be oriented in a deceptive direction.

Domaines: Optique [physics.optics]; Acoustique [physics.class-ph]; Vibrations [physics.class-ph]

Kun Tang, Chenni Xu, Sebastien Guenneau, Patrick Sebbah. Pulse dynamics of flexural waves in transformed plates. 2021. ⟨hal-03090860⟩