On the effects of suitably designed space microstructures in the propagation of waves in time modulated composites

TL;DR

This paper introduces PT-symmetric space-time microstructures that enable stable, constant-amplitude wave propagation in time-modulated composites, potentially useful for energy harvesting applications.

Contribution

It designs reciprocal PT-symmetric microstructures in 1D and 2D that stabilize wave amplitude despite time modulation and impedance mismatches, a novel approach in wave control.

Findings

Wave amplitude remains constant over time in designed microstructures

Pulse propagation is stable regardless of impedance mismatches

Potential for energy harvesting through exponential energy increase

Abstract

The amplitude of a pulse that propagates in a homogeneous material whose properties are instantaneously changed periodically in time will undergo an exponential increase, due to the interference between the reflected and transmitted pulses generated at each sudden switch. Here we resolve the issue by designing suitable reciprocal PT-symmetric space-time microstructures both in the one-dimensional and two-dimensional case, so that the interference between the scattered waves is such that the overall amplitude of the wave will be constant in time in each constituent material. Remarkably, for the geometries here proposed, a pulse will propagate with constant amplitude regardless of the impedance between the constituent materials, and for some, regardless of the wave speed mismatch. Given that the energy associated with the wave will increase exponentially in time, this creates the possibility to exploit the stable propagation of the pulse to accumulate energy for harvesting.