While developing optical interconnect technology, engineers at Hewlett-Packard Laboratories realized what they had created could be much more: a multiangle, glasses-free 3-D display technology for mobile devices. Dr. David Fattal is a member of HP’s Information and Quantum Systems Lab. “I realized that the grating coupler technology we were developing to connect optical fibers to photonic integrated circuits would be a killer technology to create multiview images from a very compact and portable screen,” he told Photonics Spectra. “It took our team only three weeks to build a first prototype. The potential for this technology seemed so great that I never looked back.” A scanning electron microscope image of the backlit surface of the HP logo shown in the picture below. It shows a close-packed array of grating pixels. The diffractive-optics-based holographic display appealed to his inner fanboy. “I’ve always been a fan of science-fiction literature and movies,” Fattal said. “I did my PhD on quantum teleportation – not yet very practical.” While the backlight the HP group used is similar to a standard LCD display, there are some important differences. “Whereas in [a] standard display the scattering centers diffuse light in all directions, in our technology they are carefully designed diffraction gratings that emit light in a very precise directional manner,” Fattal said. “The front plane is able to modulate each directional light beam independently, resulting in different moving images projected in different regions of space.” Because the display has a very wide viewing angle (up to 180º in principle), multidimensional content can potentially be seen from any direction. “Our mobile 3-D technology uses guided-wave diffractive optics to project high-resolution images at potentially very steep angles, free of geometrical off-axis aberrations,” he said. The technology “decouples the view layout from the front plane pixel layout, allowing us to render different images at very different angles while retaining the very small pixel size necessary for close-distance viewing.” A 3-D image of an HP logo in RGB, from a completely transparent substrate. The physics behind the device is solid, Fattal said. “Now the technology is entering a development phase which could take a few years. We have early applications in mind for a passively modulated backlight that might appear soon on the market.” The scientists are now “working on novel front-plane solutions to get the most out of our multiview backplane,” he said. “The way we render colors does not use color filters; hence, could lead to a display that not only images in 3-D, but is three times more efficient than commercial LCD displays today.” They also hope to enhance the display’s spatial resolution by increasing the pixel density. The research was published in Nature (doi: 10.1038/nature11972).