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DVD plus nano-rods equals security, density: researchers

A little light encryption

Polarisation used as a kind of steganography

Swinburne and Taiwanese researchers have demonstrated technology that can use a single laser beam to create 3D polarization in nanomaterials.

What’s cool about this is that they demonstrate that the polarization can be used to encrypt information – as well as expanding the storage capacity of optical media like DVDs.

As is shown in the illustration at the bottom of this story, the polarization technique – in its infancy at the moment – allows different images to be encoded in one place, showing up depending on the polarization the “read” beam uses.

Using polarization to encode information like this isn’t new: however, achieving 3D polarization using a single beam is, according to the researchers.

As the abstract in Nature states, “arbitrary three-dimensional polarization orientation of a beam hasn’t been achieved yet”.

Gold nano-rods tuned to specific wavelengths are added to the surface of the DVD, according to Swinburne’s Professor Min Gu. The rods are sensitive to the polarization of the “write-laser” – so while one polarization will align some particles in the rods, a different polarization will affect a different set of particles.

Professor Gu says the laser can be polarized “in any direction” – yielding the “arbitrary” polarization referred to in the Nature paper. This characteristic of the laser is what provides both the lift in storage density and the technique’s encryption possibilities. ®

Polarisation used as a kind of steganography

Depending on write polarization, the same area can store different images. Source: Nature

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