Holograms creating impressive three-dimensional static images are well known. Dynamic holograms switchable at video rates using data from a high-speed internet connection are not possible until now. Previously, the limiting factor was the display resolution. Holographic images require a resolution of 50,000 dpi (pixels per inch) which is 100x more than the best smartphone displays. For such a resolution one has to reduce the pixel size to half a micrometer (one-thousandth of a millimeter). However, current liquid-crystal technology does not allow for such small pixels, being limited to a few micrometers pixel size. Researchers at the University of Stuttgart have succeeded in breaking this fundamental barrier. In an interdisciplinary collaboration between Physics and Chemistry, they developed the idea to use electrically switchable plasmonic nanoantennas with dimensions of only a few hundred nanometers and made from conductive polymers.
Conductive functional polymers as suitable switchable material
Until now such materials had mostly been used for current transport in flexible displays and solar cells. In collaboration with cleanroom head Monika Ubl, Karst and Hentschel developed a process to nanostructure the metallic polymers using a combination of electron beam lithography and etching, thereby creating the plasmonic nanoantennas. The team showed that the optical appearance of the nanoantennas could be switched between that of a shiny metal and a transparent material by applying a voltage between minus and plus one volt. This switching effect works even at video rates of 30 Hertz. Despite being only a few tens of nanometers thick and less than 400 nanometers in size, the nanoantennas do the same job as the much larger and thicker liquid crystals used in current state-of-the-art technology. These new devices reach the required pixel densities of about 50.000 dpi. In the future, Prof. Harald Giessen and his team aim to address every single pixel individually, to dynamically change the holograms at will at video rates. Also, the optical properties of the polymer nanoantennas have to be shifted into the visible wavelength range, which requires collaborations with chemists and material scientists. Together with engineers, integrated and dynamically switchable optical displays and the first moving holograms could be integrated into AR/VR goggles and eventually onto smartphone screens and even televisions. Taking Moore’s law for display technology, this advance by about a factor of 100 could happen commercially around the year 2035. Reference: “Electrically switchable metallic polymer nanoantennas” by Julian Karst, Moritz Floess, Monika Ubl, Carsten Dingler, Claudia Malacrida, Tobias Steinle, Sabine Ludwigs, Mario Hentschel and Harald Giessen, 28 October 2021, Science.DOI: 10.1126/science.abj3433
