Spectral correlations in forward scattering media

Imaging deep in scattering tissues has been typically achieved by exciting non-linear optical processes thanks to broadband ultrashort laser pulses. Scattering by tissues yields so called speckle patterns and induces spectral dispersion of the beam, resulting in lengthened pulses. In this work, we demonstrate both experimentally and theoretically that deep in such forward scattering media, where most of the light has been scattered, a strong correlation unexpectedly remains between the different spectral components over very broad spectral ranges (~200nm): the 3D speckles are just axially dilated. This work represents an important step for light-beam control and efficient fluorescence collection through biological tissues.

Reference:
Chromato-axial memory effect through a forward-scattering slab
Longdi Zhu, Jacques Boutet de Monvel, Pascal Berto, Sophie Brasselet, Sylvain Gigan, and Marc Guillon
Optica 7(4), pp. 338-345 (2020)
https://doi.org/10.1364/OPTICA.382209