Time reversal through a solid-liquid interface and super-resolution

We present numerical computations that reproduce the time reversal experiments of Draeger, Cassereau and Fink (Draeger et al., 1998), where ultrasound elastic waves are time reversed back to their source with a Time Reversal Mirror (TRM) in a fluid adjacent to the solid. We also show numerically that multipathing caused by random inhomogeneities improves the focusing of the back-propagated elastic waves beyond the diffraction limit seen previously in acoustic wave propagation (Dowling and Jackson, 1990; Dowling and Jackson, 1992; Fink, 1999; Kuperman et al., 1997; Derode et al., 1995), which is called super-resolution. A theoretical explanation of the robustness of super-resolution along with several numerical computations that support this explanation is in (Blomgren et al., 2002). Time reversal with super-resolution can be used in non-destructive testing and, in a different way, in imaging with active arrays (Borcea et al., 2002). PACS numbers: 43.60.Tj, 43.60.Cg, 43.60.Rw