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Instant insight: Holography speaks volumes
29 July 2009
As the world generates more and more data, scientists strive to develop technologies to store all the information. Sřren Hvilsted, at the Technical University of Denmark, Kongens Lyngby, and colleagues at the Materials Science Institute of Aragón, Zaragoza, Spain, explain how holograms could be the answer.
We are immersed in an information age. We demand efficient data generation, transmission and storage, as well as quick access to these data. The development of cheap, high capacity data storage media has been of key relevance in this information revolution, which is exemplified by the ubiquitous world wide web. But the never-ending growth of information content in our society pushes researchers to develop new storage technologies with increasing capacities and faster data access.
Many pages of information can be stored in the same volume of azobenzene films
Azobenzene-containing polymers have drawn the attention of many research groups interested in optical storage. When irradiated with linearly polarised light (light that travels in a single plane), azobenzene molecules change their orientation to align perpendicular to the light, a property known as macroscopic optical anisotropy. This photoinduced change can be used to write information into the material, either bit by bit or by holography. But the recording laser light cannot penetrate right through thick azobenzene films because azobenzene units absorb strongly at this wavelength. Therefore, most studies have been limited to recording in films only a few micrometres thick. To fully exploit the advantages of volume holography, scientists have investigated diluting the azobenzene molecules in a polymeric matrix that is transparent at the recording wavelength. The recording light can penetrate through the samples, which can be several hundreds of micrometres thick. But the reduced azobenzene content can result in a decrease in the sensitivity and stability of the recorded holograms. Different approaches based on random copolymers, block copolymers and blends of polymers are being examined to try to fulfil application requirements.
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Link to journal article
The volume holographic optical storage potential in azobenzene containing polymers
Sřren Hvilsted, Carlos Sánchez and Rafael Alcalá., J. Mater. Chem., 2009, 19, 6641
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