Conventional optical components simply cannot achieve this kind of functionality.
- Yunuen Montelongo
Researchers from the University of Cambridge have developed a new method for making multi-coloured holograms from a thin film of silver nanoparticles, which could greatly increase the storage capabilities of typical optical storage devices.
The interference produced by the interaction of light with the nanoparticles allows the holograms to go beyond the normal limits of diffraction, or the way in which waves spread or bend when they encounter an opening or obstacle. The results were recently published in the journal Proceedings of the National Academy of Sciences.
When metallic particles have dimensions on the nanoscale, they display iridescent colours. A noted example of this phenomenon is the Lycurgus cup, which was made in the 4th century during the Roman Empire, and changes colour when held up to the light. An optical phenomenon, known as dichroism, occurs when the colour of the cup changes from green to red according to the position of the light source.
Roman artisans made the cup by incorporating nanoparticles into glass, although they would have been unaware of the specific physical characteristics responsible for the colours observed in the cup. Only in the last 20 years have scientists begun to understand this phenomenon, but they have not been able to utilise its effects in currently-available technology.
To apply this phenomenon in modern optics, an interdisciplinary team of researchers have created nanoscale metallic nanoparticle arrays that mimic the colour effects of the Lycurgus cup, to form multi-colour holograms. This breakthrough could lead to the shrinkage of standard bulky optical devices.
“This technology will lead to a new range of applications in the area of photonics, as conventional optical components simply cannot achieve this kind of functionality,” said Yunuen Montelongo, a PhD student from the Department of Engineering, who led the research. “The potential of this technology will be realised when they are mass produced and integrated into the next generation of ultra-thin consumer electronics.”
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Image: Multi-coloured holograms Credit: Yunuen Montelongo
Reproduced courtesy of the University of Cambridge
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