One-channel time-reversal in chaotic cavities: Experimental results

Experiments are presented that show the feasibility of reconstructing a point source using acoustic time-reversal with a single transmitter/receiver. The propagation medium is a closed 2-D silicon cavity with chaotic ray dynamics and negligible absorption. Injection of a short pulse at one point yields a long signal at a second one; by reversing a part of this signal, we obtain a focus at the initial injection point. The characterization of the focus was observed by scanning with an optical interferometer and by measuring the signal at the focal spot. With circular converging wavefronts, the reconstructed focus was excellent (corresponding to an aperture of 360°), but not perfect. The increase in quality of the focus with growing length of the reversed signal is described by a statistical ray model. Despite the irreversibility in classical chaos (due to strong sensitivity to initial conditions), the underlying chaotic ray dynamics is useful in this case.