Imaging with nature: Using a scattering medium as a universal scrambler for imaging by compressed sensing

[A. Liutkus et al., Sci. Rep. 5, (2014)]

The idea of compressive sensing is to acquire an image with fewer measurements than dictated by the Shannon-Nyquist theorem. In other words, an image divided into "pixels" can usually be reconstructed using fewer measurements than the total number of pixels. To do so, one needs a way to mix the information, so that any measurement contains at least a bit of information on any input element. Previous implementations of compressive sensing consisted of artificially designing hardware and a sampling procedure to generate randomness. In the present paper, the authors show that one can use a random scattering medium as a universal image scrambler. The light reflected from an image propagates through a layer of white paint and the field is measured on different receptors on the other side of the sample. By previously measuring the transmission matrix, the authors show that sparse images can be successfully reconstructed using compressed sensing techniques taking advantage of the randomness generated by multiple scattering.

Wavefront shaping: Controlling light in disordered materials

ANP2010 - Elbert van Putten
2010

Spatio-temporal control of light in complex media

PhD defense Sébastien Popoff

December 14th 2011

Control of random lasing by wavefront shaping of the pump

[N. Bachelard et al., Phys. Rev. Lett., 109, (2012)]

[M. Leonetti et al., Appl. Phys. Lett., 102, (2013)]

[N. Bachelard et al., arXiv, 1303.1398, (2013)]

[T. Hirsch et al., Phys. Rev. Lett., 111, (2013)]

While conventional lasers use mirrors to confine light in a cavity with gain to achieve spontaneous emission, random lasers take advantage of multiple scattering to trap light in a disordered medium [1]. Such lasers do not require to carefully tune the geometry of the cavity, which greatly simplifies their design. They are potentially cheaper and more robust in the presence of perturbations (temperature, vibration). The resulting emission spectrums and radiation patterns are broad but mainly uncontrolled. In recent studies [2-5] different groups demonstrated numerically and experimentally the modulation of the spatial profile of the pump to control the spectrum [2-4] or the emission pattern [5].