̽��ֱ�� of Cambridge - Yunuen Montelongo

Real-time holographic displays one step closer to reality

sc604 — Mon, 16 Mar 2015 14:00:00 +0000

Real-time dynamic holographic displays, long the realm of science fiction, could be one step closer to reality, after researchers from the ̽��ֱ�� of Cambridge developed a new type of pixel element that enables far greater control over displays at the level of individual pixels. ̽��ֱ��results are published in the journal Physica Status Solidi.

As opposed to a photograph, a hologram is created when light bounces off a sheet of material with grooves in just the right places to project an image away from the surface. When looking at a hologram from within this artificially-generated light field, the viewer gets the same visual impression as if the object was directly in front of them.

Currently, the development of holographic displays is limited by technology that can allow control of all the properties of light at the level of individual pixels. A hologram encodes a large amount of optical information, and a dynamic representation of a holographic image requires vast amounts of information to be modulated on a display device.

A relatively large area exists in which additional functionality can be added through the patterning of nanostructures (optical antennas) to increase the capacity of pixels in order to make them suitable for holographic displays.

“In a typical liquid crystal on silicon display, the pixels’ electronics, or backplane, provides little optical functionality other than reflecting light,” said Calum Williams, a PhD student at Cambridge’s Department of Engineering and the paper’s lead author. “This means that a large amount of surface area is being underutilised, which could be used to store information.”

Williams and his colleagues have achieved a much greater level of control over holograms through plasmonics: the study of how light interacts with metals on the nanoscale, which allows the researchers to go beyond the capability of conventional optical technologies.

Normally, devices which use plasmonic optical antennas are passive, meaning that their optical properties cannot be switched post-fabrication, which is essential for real-world applications.
Through integration with liquid crystals, in the form of typical pixel architecture, the researchers were able to actively switch which hologram is excited and there which output image is selected.

“Optical nanoantenas produce a strong interaction with light according to their geometry. Furthermore, it is possible to modulate this interaction with the aid of liquid crystals,” said co-author Yunuen Montelongo, a PhD student at the Department of Engineering, who, along with Williams, is a member of the CMMPE group.

̽��ֱ��work highlights the opportunity for utilising the plasmonic properties of optical antennas to enable multi-functional pixel elements for next generation holographic display technologies.

Scaling up these pixels would mean a display would have the ability to encode switchable amplitude, wavelength and polarisation information, a stark contrast to conventional pixel technology.

Researchers from the ̽��ֱ�� of Cambridge have designed a new type of pixel element and demonstrated its unique switching capability, which could make three-dimensional holographic displays possible.

A large amount of surface area is being underutilised, which could be used to store information

Calum Williams

Rendered schematic of holographic pixels in operation showing switching states

̽��ֱ��text in this work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page. For image rights, please see the credits associated with each individual image.

Yes

Nanotechnology used to create next-generation holograms for information storage

sc604 — Thu, 28 Aug 2014 07:23:34 +0000

Researchers from the ̽��ֱ�� 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.

̽��ֱ��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. ̽��ֱ��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. “ ̽��ֱ��potential of this technology will be realised when they are mass produced and integrated into the next generation of ultra-thin consumer electronics.”

Using a single thin layer of silver, Montelongo and his colleagues patterned colourful holograms containing 16 million nanoparticles per square millimetre. Each nanoparticle, approximately 1000 times smaller than the width of a human hair, scatters light into different colours depending on its particular size and shape. ̽��ֱ��scattered light from each of the nanoparticles interacts and combines with all of the others to produce an image.

̽��ֱ��device can display different images when illuminated with a different colour light, a property not seen before in a device of this type. Furthermore, when multiple light sources are shone simultaneously, a multi-colour image is projected.

These holographic devices are between 10 and 100 times smaller than just one of the millions of pixels used to produce a colour image on a typical laptop screen, yet they project a complete multi-colour image to the eye. This is possible through plasmonics: the study of how light interacts with metals on the nanoscale, which allows the researchers to go beyond the capability of conventional optical technologies.

“This hologram may find a wide range of applications in the area of displays, optical data storage, and sensors,” said PhD student Calum Williams, a co-author of the paper. “However, scalable approaches are needed to fulfil the potential of this technology.”

Currently, the team is exploring various optical mechanisms involved in the light-matter interaction at nanoscale. ̽��ֱ��future research will involve the construction of three-dimensional dynamic displays for consumer electronics and the researchers are already looking into tuning these devices for reconfigurable display technologies.

Holograms made of tiny particles of silver could double the amount of information that can be stored in digital optical devices, such as sensors, displays and medical imaging devices.

Conventional optical components simply cannot achieve this kind of functionality

Yunuen Montelongo

Multi-coloured holograms

Yes

Nanotubes used to create smallest ever hologram pixels

bjb42 — Fri, 21 Sep 2012 15:17:31 +0000

Scientists have generated holograms from carbon nanotubes for the first time, which could lead to much sharper holograms with a vastly increased field of view.

̽��ֱ��researchers from the ̽��ֱ��’s Centre of Molecular Materials for Photonics and Electronics (CMMPE) have harnessed the extraordinary conductive and light scattering abilities of these tubes - made from several sheets of carbon atoms rolled into a cylinder - to diffract high resolution holograms.

Carbon nanotubes are one billionth of a metre wide, only a few nanometres, and the scientists have used them as the smallest ever scattering elements to create a static holographic projection of the word CAMBRIDGE.

Many scientists believe that carbon nanotubes will be at the heart of future industry and human endeavour, with anticipated impact on everything from solar cells to cancer treatments, as well as optical imaging. One of their most astonishing features is strength - about 100 times stronger than steel at one-sixth the weight.

̽��ֱ��work on using these nanotubes to project holograms, the 2D images that optically render as three-dimensional, has been published in the journal Advanced Materials.

“Smaller pixels allow the diffraction of light at larger angles - increasing the field of view. Essentially, the smaller the pixel, the higher the resolution of the hologram,” said Dr Haider Butt from CMMPE, who conducted the work along with Yunuen Montelongo.

“We used carbon nanotubes as diffractive elements - or pixels - to produce high resolution and wide field of view holograms.”

̽��ֱ��multi-walled nanotubes used for this work are around 700 times thinner than a human hair, and grown vertically on a layer of silicon in the manner of atomic chimney stacks.

̽��ֱ��researchers were able to calculate a placement pattern that expressed the name of this institution using various colours of laser light - all channelled out (scattered) from the nano-scale structures.

For Haider Butt this is just the start - as these pixels and their subsequent displays are not only of the highest resolution, but ultra-sensitive to changes in material and incoming light.

"A new class of highly sensitive holographic sensors can be developed that could sense distance, motion, tilt, temperature and density of biological materials,” said Butt.

“What’s certain is that these results pave the way towards utilising nanostructures to producing 3D holograms with wide field of view and the very highest resolution.”

For the researchers, there are two key next steps for this emerging technology. One is to find a less expensive alternative to nanotubes, which are financially prohibitive: “Alternative materials should be explored and researched, we are going to try zinc oxide nanowires to achieve the same effects.”

̽��ֱ��other is to investigate movement in the projections. Currently, these atomic scale pixels can only render static holograms. Butt and his team will look at different techniques such as combining these pixels with the liquid crystals found in flat-screen technology to create fluid displays - possibly leading to changeable pictures and even razor-sharp holographic video.

A breakthrough in the use of carbon nanotubes as optical projectors has enabled scientists to generate holograms using the smallest ever pixels.

These results pave the way towards utilising nanostructures to producing 3D holograms with wide field of view and the very highest resolution.

Haider Butt

Dr Haider Butt

Hologram

This work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page.

Yes