Researchers at Purdue University have developed a technology that aims to replace Morse code with colored “digital characters,” helping to modernize optical storage media. The advancement, the researchers said, will help with the expansion of remote data storage during and after the COVID-19 pandemic. Rather than using the dots and dashes of Morse code, the researchers’ approach encodes information in the angular positions of tiny antennas, which allows them to store higher amounts of 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 Alexander Kildishev, associate professor of electrical and computer engineering in Purdue’s College of Engineering. “We map the antenna angles into colors, and the colors are decoded.” In the making of a Blu-Ray disc, for example, a silicon stamper replicates the same dot and dash format pressed into the final disc. A thin nickel coating is then added to get a negative stamp. “Our metasurface-based ‘optical storage’ is just like that,” said Di Wang, a former Ph.D. student who fabricated the prototype structure. “Whereas in our 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.” The new method also increases the data 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.” In the future, the technology could see use in security tagging and cryptography. The team is looking to partner with interested parties in the industry to further develop the technology. The research was published in Laser & Photonics Reviews (www.doi.org/10.1002/lpor.202000343).