Chromato-axial memory effect through a forward-scattering slab

Light propagation through scattering samples involves long optical path lengths typically resulting in short spectral correlation widths. Here, we demonstrate experimentally and theoretically a chromato-axial memory effect through volumetric forward-scattering slabs of thickness lying in the range between the scattering mean free path and the transport mean free path: a spectral shift of the impinging collimated beam results in an axial homothetic dilation of the speckle pattern over large spectral widths. The center of the homothety is shown to lie at a virtual plane located at 1 / ( 3 n ) of the slab thickness L , before the output surface. These results provide new tools to blindly control wavefields through scattering samples.