Laser Printing a Nanoscale Mona Lisa Could Revolutionize Reproduction Technology

The field of plasmonics has offered some pretty exciting technologies over the past few years, including improved photovoltaics, LEDs, and a host of other optoelectronic applications—most notably photonic circuits that duplicate what electronic ICs can do.

Now researchers at the Technical University of Denmark (DTU) have leveraged plasmonics in a way that may completely revolutionize laser printing by creating a laser printer capable of producing images with 120,000 dots-per-inch resolution. Just to demonstrate how revolutionary the technology is, the DTU researchers reproduced a color image of the Mona Lisa in a space smaller than the footprint taken up by a single pixel on an iPhone Retina display.

In the research, which was published in the journal Nature Nanotechnology,  the Denmark researchers were able to achieve this remarkable resolution using plasmonic nanostructures in place of dyes. However, the researchers added a bit of a twist to traditional techniques for doing this that could make the process far more scalable.

Instead of using methods such as e-beam lithography (EBL) or focused ion beam (FIB), neither of which can be scaled to pre-design and print the plasmonic nanostructures, the researchers went with a process known as laser post-writing. The process starts with a surface that has been prepped by adding rows and columns of nanoscale structures, each with a diameter of 100 nanometers. This nanostructured surface is then covered by a 20-nm-thick sheet of aluminum.  At this point, the laser post-writing is introduced. A laser pulse is aimed at each column, heating it up locally and causing it to melt and deform.

The intensity of the laser pulse determines the level of deformation, and consequently, the colors that the column reflects. A low-intensity laser pulse causes little deformation; the colors of blue and purple are reflected. When the laser pulses are more intense and the deformation more extreme, the deformed structure reflects orange and yellow colors.

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