- T. Chaigne, O. Katz, A.C. Boccara, M. Fink, E. Bossy, S. Gigan, Controlling light in scattering media noninvasively using the photo-acoustic transmission-matrix, Nature Photonics, 8, 58–64 (2014) NATPHOT ARXIV
- T. Chaigne, J. Gateau, O. Katz, E. Bossy, S. Gigan, Light Focusing and Two-Dimensional Imaging Through Scattering Media using the Photoacoustic Transmission-Matrix with an Ultrasound Array, Optics Letters, Vol. 39, Issue 9, pp. 2664-2667 (2014)
Photoacoustic focusing and imaging inside a scattering medium (collab. E. Bossy @ Institut Langevin)
The ability to use wavefront shaping techniques for deep biological imaging, cannot rely on access to both side of a medium. One wants to work from one side only, and cannot place a detector inside the medium. Guiding light inside a complex medium by wavefront shaping requires a “guide star” or “beacon” to measure light intensity in depth. Acoustics wave, that propagates almost undisturbed in biological tissues are good candidates to probe light intensity. In our approach, we rely on photoacoustics, a technique where local light absorption deep inside a tissues generates an acoustic signal that can be detected and localized from the outside using a transducer. We demonstrate the measurement of a photoacoustic transmission matrix, that allow focusing in depth.
O.Katz, P.Heidmann, M.Fink, S. Gigan, Non-invasive real-time imaging through scattering layers and around corners via speckle correlations, Nature Photonics, 8, 794 (2014) link
single shot imaging behind scattering layers
For a surface scatterer or a thin scattering system, there is an angular “memory effect” of the speckle. Consequently, all information is not completely lost when the image of an object propagates through such a medium. Using a technique known as “phase-retrieval”, we show how we can recover the object from a single speckle image taken on a CCD, without calibration nor wavefront shaping.
- S.Schott, J.Bertolotti, J.F. Léger, L. Bourdieu, S. Gigan, Characterization of the angular memory effect of scattered light in biological tissues, arXiv:1502.00270 ARXIV
- J. Binding, J. Ben Arous, J.F. Léger, S. Gigan, A.C. Boccara, L. Bourdieu, In vivo rat brain refractive index measurement using full-field OCT and consequences for two photon microscopy, Optics Express 19, 4833 (2011) OE
Adaptive optics in biological tissues
(collab. L. Bourdieu @IBENS, C. Boccara @institut Langevin)
we explore the possibility of improving image quality for deep microscopy in biological tissues, which are typically both scattering and aberrating. Unfortunately, conventional wavefront sensing techniques are not usable anymore. We use a conventional adaptive optics setup, with a traditional deformable mirror, and optimize deep imaging using the image quality itself as a metric.