Noninvasive light focusing in scattering media using speckle variance optimization

The propagation of a laser beam through a scattering medium generates a complex figure of interference, known as a speckle pattern.Over the past decade, many wavefront shaping techniques have emerged to manipulate this scattered light, in particular refocus it to a diffraction-limited spot as it exits the medium.
However, performing this operation in a non-invasive way is challenging, especially with a linear signal such as fluorescence. By optimizing the variance of the fluorescent signal emitted by a set of fluorescent beads, hidden inside the scattering medium, the authors (Antoine Boniface, Baptiste Blochet, Jonathan Dong and Sylvain Gigan) were able to focus the light on one of them.
This new approach should generalize to a large variety of incoherent contrast mechanisms and holds interesting prospects for deep biological imaging.

Read the full article :

Scheme of the experiment (A.). Images respectively recovered in transmission (B.) and reflection (C.).


Legend : Speckle emitted by a set of fluorescent beads