Debasmita Banerjee
Debasmita Banerjee
Instrumentation
14 May 2016

Nanotechnology To Make Holographic Applications More Secure And Efficient

Since its birth, holograms have been extensively used to serve security systems and related purposes. The making of a hologram, dissecting it to pieces and again rejoining the blocks involves a steady orientation of lenses which encodes the information with depth perception that could be deciphered later according to requirement.

It’s hard to imagine a 21st century city running smooth without an immense use of holograms, small or big sized 2D cards with 3D engraved pictures that are present in credit cards, grocery objects, books, biomedical devices and in other objects requiring retrievable information to be stored.

In terms of concealing product information, these sticker based fancy stuffs were up to the mark, until technology escalated beyond imagination. Even a previously measured safe encryption suffered from threat and these tools became fragile. Researchers initialized various approaches to hit the safest and complex path, among which nanotechnology had an answer in store for them. A research team from the Harvard John A. Paulson School of Engineering and Applied Sciences had recently forced polarization to concise holograms, comprising of tiny light-polarization sensitive nanostructures to generate numerous ones depending upon the polarization configuration of light.

Holograms_projected_on_White_Screen International Year of Light Logo Hologram while projected on White Screen

With the help of such advancements, scientists are now trying to devise anti-fraud holograms that involve best security practices. Nanotechnology always comes with some common advantages, one being its nano-scale working. When the scale is compressed to an ultra-small level, it escalates the degree of confinement, which in turn helps in producing a series of results on the modulation. As polarization is fed, another dimension pops up to store and retrieve more number of images. Professor Federico Capasso, one of the project authors has mentioned that the latest system is extremely efficient as very little light is lost during production.

While giving explanation, the team mentioned that a hologram differs from a digital image in terms of their recording capacity and technicality. A digital image records only the intensity of light while a hologram manages to capture the phase of the light and so it appears as three dimensional. There are several states of polarization available, among which linearly polarized light has constant direction of vibration, but in circularly polarized light, it rotates clockwise or counterclockwise. The nano-structured silicon superpixels were designed on a glass substrate in such a way so that the susceptible nano structure encodes information on the basis of the rotational direction of circular polarization.

hologram_3D_IYL_logo
2015 IYL logo in hologram format (authorised by SPIE, OSA and UNESCO)

Antonio Ambrosio, a research scientist at the Capasso Lab and a co-author of the related paper explained that the rotational direction helps to add a secure anti-counterfeiting property. Suppose, the rotational direction property is used wisely it would generate a certain series of images while the other would put up something different from a matching code. As the system is compact, it could be used to devise portable projectors, 3D movies and other wearable optics.

Also, the current research requires only a single layered dielectric surface instead of a series of instruments such as beam splitters, polarizers and wave plates. As the primary work is done, the team is planning to commercialize it. The work was supported by the Air Force Office of Scientific Research, Google Inc. and Thorlabs Inc., and was published in the Science Advances journal.

Source: Havard | Science Advances

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