Novel display technologies aim to provide the user an ever-increasing immersive experience. In this regard, displaying true 3D images that can be seamlessly integrated with the real world is a long-sought dream that hold potential to revolutionize the way we receive and interact with information. In order to generate truly 3D images, i.e. holograms, one needs a device that allows to control one of the fundamental properties of light, namely, its phase. While such devices exist (they are the so-called Spatial Light Modulators), current liquid-crystal based technology has a very strong limitation. Specifically, the 3D images that can be generated with them can only be seen from a very narrow range of viewing angles, which strongly hinders the experience. Importantly, this limitation, which stems from the large pixel size of these devices, is not one of engineering nature but rather a physical limitation imposed by the principle used to manipulate the light. Therefore, to overcome it, a radically different idea is needed.
In this work, the team of researchers from IMRE’s Advanced Optical Technologies department (Shi-Qiang Li, Xuewu Xu, Rasna Maruthiyodan Veetil, Vytautas Valuckas, Ramón Paniagua-Domínguez and Arseniy Kuznetsov) has put forward a new approach to dynamically manipulate the phase of light with ultra-small pixel sizes. Instead of using the modulation of phase acquired by light when travelling through a medium, as is the case in liquid-crystal-based devices, they used a set of tiny nanostructures (smaller than the wavelength of light), so-called nanoantennas, that resonate when illuminated by light.
In a similar way that TV or cell phone antennas do with other electromagnetic waves, these nanostructures can efficiently collect and re-emit visible light. In this process, however, they can alter the phase of the re-emitted light, opening the possibility to control its wavefront and ultimately, to generate holographic images with unparalleled viewing angle and unprecedented resolution. By surrounding these nanoantennas by a thin liquid crystal, this can be done dynamically, opening the door to realize full-depth, true 3D holographic displays that do not require any goggles or special equipment to be viewed. Besides its application in displays, the concept developed in this work can be applied in 3D mapping and ranging, telecommunications or bioimaging, etc.
Shi-Qiang Li et al., "Phase-only transmissive spatial light modulator based on tunable dielectric metasurface", Science 364(6445), 1087-1090 (2019)
Link to online version of paper in Science.