Graphene brings 3-D holograms clearer and closer

From mobile phones and computers to television, cinema and wearable devices, the display of full colour, wide-angle, 3D holographic images is moving ever closer to fruition, thanks to international research featuring Griffith University ("Athermally photoreduced graphene oxides for three-dimensional holographic images"). Led by Melbourne's Swinburne University of Technology and including Dr Qin Li, from the Queensland Micro- and Nanotechnology Centre within Griffith's School of Engineering, scientists have capitalised on the exceptional properties of graphene and are confident of applications in fields such as optical data storage, information processing and imaging. "While there is still work to be done, the prospect is of 3D images seemingly leaping out of the screens, thus promising a total immersion of real and virtual worlds without the need for cumbersome accessories such as 3D glasses," says Dr Li. First isolated in the laboratory about a decade ago, graphene is pure carbon and one of the thinnest, lightest and strongest materials known to humankind. A supreme conductor of electricity and heat, much has been written about its mechanical, electronic, thermal and optical properties. "Graphene offers unprecedented prospects for developing flat displaying systems based on the intensity imitation within screens," says Dr Li, who conducted carbon structure analysis for the research. "Our consortium, which also includes China's Beijing Institute of Technology and Tsinghua University, has shown that patterns of photo-reduced graphene oxide (rGO) that are directly written by laser beam can produce wide-angle and full-colour 3D images. "This was achieved through the discovery that a single femtosecond (fs) laser pulse can reduce graphene oxide to rGO with a sub-wavelength-scale feature size and significantly differed refractive index. "Furthermore, the spectrally flat optical index modulation in rGOs enables wavelength-multiplexed holograms for full colour images." Researchers say the sub-wavelength feature is particularly important because it allows for static holographic 3D images with a wide viewing angle up to 52 degrees. Such laser-direct writing of sub-wavelength rGO featured in dots and lines could revolutionise capabilities across a range of optical and electronic devices, formats and industry sectors. "The generation of multi-level modulations in the refractive index of GOs, and which do not require any solvents or post-processing, holds the potential for in-situ fabrication of rGO-based electro-optic devices," says Dr Li. "The use of graphene also relieves pressure on the world's dwindling supplies of indium, the metallic element that has been commonly used for electronic devices. "Other technologies are being developed in this area, but rGO looks by far the most promising and most practical, particularly for wearable devices. The prospects are quite thrilling."