Purdue researchers have created technology aimed at replacing Morse code with colored “digital characters” to modernize optical storage. They are confident the advancement will help with the explosion of remote data storage during and after the COVID-19 pandemic.

The proposed anisotropic metasurface from Purdue University innovators has significant potential for high-density optical data storage, dynamic color image display, and encryption. (Image courtesy of the researchers)

Morse code has been around since the 1830s. The familiar dots and dashes system may seem antiquated given the amount of information needed to be acquired, digitally archived, and rapidly accessed every day. But those same basic dots and dashes are still used in many optical media to aid in storage.

The new technology is aimed at modernizing optical digital storage. This advancement allows for more data to be stored and for that data to be read at a quicker rate. Rather than using the traditional dots and dashes as commonly used in these technologies, the information is encoded in the angular position of tiny antennas, allowing them to store more data per unit area.

“The storage capacity greatly increases because it is only defined by the resolution of the sensor by which you can determine the angular positions of antennas,” said Professor Alexander Kildishev. “We map the antenna angles into colors, and the colors are decoded.”

Not all optical data storage media needs to be laser-writable or rewritable. The majority of CDs, DVDs, and Blu-Ray discs are “stamped” and not recordable at all. This class of optical media is an essential part of disposable cold storage with a rapid access rate, long-lasting shelf life, and excellent archival capabilities.

The making of a Blu-Ray disc is based on the pressing process, where the silicon stamper replicates the same dot-and-dash format the final disc is getting. A thin nickel coating is then added to get a negative stamp. The Blu-Rays, as well as DVDs and CDs, are just mass-produced.

According to the researchers, their metasurface-based "optical storage" is just like that. Although in their demo prototype, the information is ‘burnt in’ by electron-beam lithography, it could be replicated by a more scalable manufacturing process in the final product.

This new development not only allows for more information to be stored but also increases the readout rate. “You can put four sensors nearby, and each sensor would read its own polarization of light,” Kildishev said. “This helps increase the speed of readout of information compared to the use of a single sensor with dots and dashes.”

To continue developing application capabilities like security tagging and cryptography, the team is looking to partner with interested parties in the industry.

For more information, contact Alexander Kildishev at This email address is being protected from spambots. You need JavaScript enabled to view it..


Photonics & Imaging Technology Magazine

This article first appeared in the September, 2021 issue of Photonics & Imaging Technology Magazine.

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