COPS scientists were the first to demonstrate how to focus light through strongly scattering complex media, such as opaque layers of nanoparticles like ZnO or TiO2 (“paint”). Therefore, we developed a novel wavefront shaping method capable of controlling light in thousands of incident modes. The shaped scattered light forms a focus up to 1000 times brighter than the normal diffuse transmission, see Figure below.


Focusing light through an opaque material. Left: When we shine a plane light wave on an opaque white layer of paint, the transmitted light shows a dim, disordered interference pattern known as speckle. Right: By shaping the incident wavefront to match the scattering inside the material, the transmitted light shows an intense focus. Remarkably, the background speckle also becomes brighter, in agreement with mesoscopic theory (click here).

We have used wave front shaping to selectively couple light to the open transport eigenchannels, specific solutions of Maxwell’s equations that the complex medium fully transmits (surprisingly!) Our results are the first direct confirmation of the existence of these open channels, which are a key concept in transport theory in condensed matter and mesoscopic physics. Mesoscopic random matrix theory is found to be in excellent quantitative agreement with our experimental results.

Our wavefront shaping method has inspired many groups worldwide to develop innovative trapping and imaging techniques. A good overview can be found in our review with our Paris-Tech colleagues in Nature Photonics.

Contrary to the general belief that scattering of light always leads to a deterioration of image quality, we have developed a scattering lens that resolves structures with an unprecedented optical resolution. By carefully manipulating the phase of the illumination beam, we turn the scattered light into a scanning nano-focus in the object plane of our lens. Raster-scanning this focus over our objects yields a high resolution image at sub-100 nm resolution; much better than what is possible with even the most expensive commercial microscope objectives(!) The scattering lens can be combined with a wide range of existing microcopy techniques to get even higher resolutions, click here.