Interferometric experiments on the transmission matrix of diffusive neutral inclusions

By using tailored disorder in the regime of diffusive light propagation, core-shell cloaking structures have previously been presented. These structures make the cloak and an arbitrary interior nearly indistinguishable from the diffusive surrounding. This statement holds true for all incident polarizations of light, a broad range of incident directions of light in three dimensions, and a broad range of visible wavelengths. Here, by performing interferometric transmission-matrix experiments, we investigate the statistical wave properties of miniaturized versions of such structures. By using singular-value decomposition, we derive the eigenchannels and eigenvalues to assess the degree of wave correlation among multiply scattered waves. We find small but significant differences in the eigenvalue distributions, suggesting that the degree of wave correlation is lower for the neutral inclusion than for a homogeneously disordered reference sample, which corresponds to the surrounding of the neutral inclusion. Likewise, we find similar differences between optically inspecting the core-shell neutral inclusion and its spatial neighborhood. These differences allowus to reveal the neutral inclusion due to different statistics of the underlying random walks of light.