Nano-sized audio recordings could signal storage breakthrough

[Reefa]

The motion picture industry employed optical sound-on-film recording for over 80 years, at least before digital recording took over. Now a team of researchers may have discovered a new way of storing data optically on a much smaller scale — by way of recording a “nano piano” onto a plasmonic film substrate for the first time.

The group, led by University of Illinois MechSE associate processor Kimani Toussaint, used an array of gold, pillar-supported, bowtie nanoantennas (pBNA) to store audio clips on a chip with dimensions that are approximately equivalent to the thickness of human hair. That gives it about 5,600 times the storage capacity compared with magnetic film.

Using this method, you could store sound information either as a varying-intensity waveform or a frequency-varying waveform. To test it, the group stored eight musical notes, such as middle C, D, and E, on a pBNA chip and then played them back to form a small tune. The result: a plasmonic musical keyboard, or “nano piano.” The photo below shows a concept of the nano piano playing “Twinkle, Twinkle, Little Star.” The pillar-supported bowtie nanoantennas (bottom left) can be used to record distinct musical notes, as shown in the experimentally obtained dark-field microscopy images (bottom right).

A concept of the nano piano playing “Twinkle, Twinkle, Little Star.”

“Our approach is analogous to the method of ‘optical sound,’ which was developed circa 1920s as part of the effort to make ‘talking” motion pictures,'” the team said in a statement. That process normally goes roughly like this: An audio pickup (such as a microphone) electrically modulates a lamp source. Variations in the intensity of the light source is encoded on semi-transparent photographic film. You then decode it by illuminating the film with the same light source, and picking up changes in the light transmission on an optical detector, which in turn may be connected to speakers.

What this research team did was use the pBNAs to do what the photographic film does in the above example. They wrote the audio information directly into nanostructures using a laser in an optical microscope, and then played it back using the same microscope. by imaging the waveform onto a digital camera and processing it. Previously, the same team showed that pBNAs allow for reduced thermal conduction compared with standard bowtie nanoantennas, and can heat up when irradiated with low-power laser light. That in turn subtly melts the gold and changes the overall optical response.

The possibilities extend beyond audio recording on a nano scale. “Data storage is one interesting area to think about,” Toussaint said. “For example, one can consider applying this type of nanotechnology to enhancing the niche, but still important, analog technology used in the area of archival storage such as using microfiche. In addition, our work holds potential for on-chip, plasmonic-based information processing.”

And this is all in the analog realm; there’s plenty of potential for digital storage. “A characteristic property of plasmonics is the spectrum,” said Hao Chen, a former postdoc in Toussaint’s PROBE laboratory and the first author of the paper. “Originating from a plasmon-induced thermal effect, well-controlled nanoscale morphological changes allow as much as a 100-nm spectral shift from the nanoantennas. By employing this spectral degree-of-freedom as an amplitude coordinate, the storage capacity can be improved. Moreover, although our audio recording focused on analog data storage, in principle it is still possible to transform to digital data storage by having each bowtie serve as a unit bit 1 or 0.” By modifying the size of the bowtie, Chen said, it’s feasible to further improve the storage capacity.

http://www.extremetech.com/extreme/201913-nano-sized-audio-recordings-could-signal-storage-breakthrough