David Fattal, one of France's top ten innovators

David Fattal, 33 years old: 3D images and video on mobile terminals, without glasses or the hologram revolution on smartphones.

David Fattal discovered his fascination with physics while studying string theory at the Ecole Polytechnique, 15 kilometres from Paris (France). This old dream of reconciling quantum mechanics and general relativity theory might have seemed unattainable, yet after graduating in theoretical physics, this young engineer, determined to discover the more experimental aspect of this science, turned to new academic territories - those of quantum information - which led him thousands of miles away from home, to Stanford University in the United States.

From the beginning of his career, Fattal felt attracted to the study of light, aware of the possibilities offered by its compression. He was amazed by the "peculiar, almost magical" properties that light acquires when it interacts with microscopic structures. As he explains himself, a "strong intuition" came to him during his doctorate at a North American university, leading him to decipher "the phenomena of resonance in planar dielectric structures" in order to control the emission, propagation and absorption of light.

During these years, Fattal not only deepened its knowledge of these processes, but also became aware of the potential applications. The fields of quantum information and optical interconnections thus benefited greatly from his discoveries, which have led to more than 40 patents - some of which have been licensed to major optical connector companies - and several publications in scientific journals. Far from being satisfied with his achievements, Fattal was determined to move forward when he joined HP's Nanophotonics Laboratory in 2005: "I was convinced that I could use my experience to design something important, non-intuitive and with immediate industrial application," he says.

Finally, in 2011, an idea is taking shape. "I thought I could solve the big problems of digital holography by using externally modulated grid couplers as directional pixels," says Fattal. Since that day, the team he leads has been focused on one goal: to create a system that allows viewing 3D video without glasses from a mobile device on a thin and compact screen, and that provides the viewer with a stereoscopic experience no matter from what angle they look at the images.

To achieve this goal, the technology designed by the 33-year-old physicist integrates two elements: a backlight system and an external modulator similar to the liquid crystal display (LCD) screens of many existing phones, cell phones or tablets. The backlight system is made of a very thin sheet of glass just a few millimetres wide. Underneath this sheet, from the side parts, a series of LED bulbs emit light towards the inside of the glass in a very precise direction. Fattal's team achieves this level of precision by using various methods to obtain a parallel beam of rays from the LED light source. Using these methods and the techniques of cutting and polishing the side edges of the sheet, the light is guided to various pixels that have been 'recorded' on the surface of the glass.

The light modulation capability of these pixels is one of Fattal's specialities. His ability to control light via 'dielectric grids' - a concept he developed during his work on optical interconnections - now enables him to apply this technique in the field of three-dimensional images for mobile terminals.

Fattal has thus created its first prototypes which function as follows: each of the pixels recorded on the surface of the backlight system is an optical 'diffraction grid' manufactured via photolithography which disperses light in a controlled manner, generating a 'light field' towards the image viewing area.

This is where the external modulator (a few tens of microns in size) comes into play. Placed on the backlight system, it is capable of adjusting the intensity transmitted by each individual light beam and generating an image that can be composed of the three primary colours (green, red and blue). "The modulator has a pass factor of a few tens of microns, whereas a digital holographic terminal requires a pass factor of less than one micron," explains Fattal. This means that his terminal can handle higher image processing rates and offer video animations (they have published tests at 30 frames per second).

Another advantage of this technology is that it does not require the use of colour filters to obtain images or animations, which makes for a totally transparent terminal and improves the energy efficiency of the display compared to current LCDs, which, according to Fattal, "waste 66 percent of the light just by filtering colours".

Fattal's team presented its first prototypes in a publication in the scientific journal Nature. These are various terminals made with low-cost materials and standard procedures. These are currently capable of generating a static image of any colour or basic three-dimensional animated sequences, such as a globe rotating on its axis.

In the opinion of Christophe Delerue, director of research at the CNRS, professor of physics at ISEN and member of the jury of the MIT Technology Review Innovators under 35 years old France awards, this young man "has designed revolutionary innovations based on the use of the interaction between light and nanostructures" and whose applications in 3D visualization "should be numerous and reach a wide audience".

Fattal recognizes that developing his technologies within HP is a real competitive advantage in that he has had the freedom to quickly turn his initial idea into working prototypes. His next challenge is to convert his prototypes into real products with real market appeal: "I'm going to fight to see the first commercial applications as decorative elements this year, and then to bring video viewing to a wide range of mobile devices to market," says the innovator.

Article written by Elena Zafra / © MIT Technology Review March 2013

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