As unbelievable as it may sound, an ancient Roman goblet holds the key to modern 3D hologram technology. The 4th century cup now resides in the British Museum in London. It is carved from a single block of glass and framed with the story of King Lycurgus and his conflict with Dionysus, the god of wine. The cup changes color from jade green to ruby red when a light shines through it. Modern scientists are learning how to replicate the cup’s technology to create 3D holograms and vast optical storage systems.
The Lycurgus cup, a glass drinking goblet, was created by the Romans using nanoparticles. The glass changes color depending on the light and, possibly, on what liquid it holds. The early Romans did not understand nanotechnology, but they had an idea about combining metal and glass and were able to make it work. They ground gold and silver into tiny particles and embedded them in the liquid glass. Researchers estimate that they were able to grind the particles down until 1,000 of them would fit into a grain of sand. The cup was created approximately 1,700 years ago with processes which scientists are just beginning to understand and be able to replicate today. The color change from green to red is caused when photons excite the electrons in the metal particles. The cup’s properties were noticed when it was brought to the museum in the 1950s, but it was not until the 1990s that scientists learned how the cup works. Now, nanoparticles and nanocrystals are being studied assiduously in order to advance holograms and information storage.
Embedding materials with nanoparticles can change and expand their properties. Nanotechnology could bring major advances in medical, optical and electronic fields. Nanoparticles can better utilize low-energy light sources, make solar cells more efficient, and optimize advanced sensors. Nanoparticles need to be embedded in a solution in order to be fixed into a matrix which can be exploited. Mixing them into liquid glass which then solidifies into a permanent shape allows researchers to manipulate the particles into something usable. Finding the correct particles and the correct mixture of glass can be a trial and error process, but it is starting to reap success. Scientists at the University of Adelaide were able to embed nano-diamonds into glass to capture single photons.
A team of researchers at the University of Cambridge in the U.K. led by Yunuen Montelongo has found a way to use surface plasmon resonance to construct holograms. Similar to the Lycurgas cup, silver nanoparticles are used to scatter light and create color-changing patterns. This technology could have applications in 3D displays and information storage devices.
Montelongo’s team proved it is possible to create multi-color holograms from a single plane and to place them over a curved surface. So far, holograms such as those used for security on credit cards have been single color and only 2D. The holograms produced by the optical scattering of the silver nanoparticles can take holograms to a whole new level. The size and shape of the silver nanoparticles can change the way light is scattered. In addition, two different types of nanoparticles can be used to carry information independently. Montelongo states, “Because of the nature of this phenomenom, it has been possible to demonstrate, for the first time, a hologram that projects color images in 180 degrees. This projection is so wide that it is not even possible to display it on a plane, and a diffusive sphere should be used.” The research could be key to producing dynamic 3D projections. It can also greatly expand the storage capabilities of CDs, DVDs and Blu-Ray.
The paper was published in The Proceedings of the National Academy of Sciences of the United States and is titled, Plasmonic Nanoparticle Scattering for Holograms. The abstract states that it represents an original approach to holograms. However, Montelongo told Phys.org, “This experiment is inspired by the very unique properties shown by the Lycurgus cup.” A 1,700 year old historical artifact has inspired technological advancement; an ancient Roman goblet holds the key to modern 3D holograms.
By: Rebecca Savastio