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SYLVAIN GIGAN 'Can One See Through Opaque Material?'

20100531-Sylvian-Gigan_157pxSYLVAIN GIGAN
Laboratoire d'Optique, Paris, FRANCE
ESPCI, Cergy-Pontoise Cedex, FRANCE
Seminar, May 31, 2010, 12:00. Seminar Room

When light propagates in a disordered material, information is seemingly lost. This is why we can't see through most biological samples. Nonetheless, propagation of waves in complex media give rise to a lot of interesting physics, ranging from photonic crystals to Anderson localization, from strong coupling to quantum correlations.

Recently, a method has been proposed by A. Mosk and coworkers to focus light through a multiple scattering material, using a spatial light modulator as a tool to shape the incoming beam to obtain a maximal interference on a speckle spot of the output speckle pattern. The result is a diffraction limited spot which can be several hundred time brighter than the rest of the speckle.

However, there is a much more general approach to the problem of imaging and controlling light in a random medium. It consists in measuring the transmission matrix, i.e. the matrix linking the amplitude of the input to the output modes of the multiple scattering material. This approach not only gives several new possibilities for imaging, but also allow direct insight on the material itself.

I will detail our original method, which has allowed us to measure the transmission matrix of a thin opaque slab of ZnO powder. I will show how we can focus light, but also recover a simple image from multiply scattered light and measure and exploit the transmission channels of the material. We believe that this method is very promising, both for imaging application, and for the study of wave propagation in complex materials.
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