Light caught among crystals on macroscopic scale

Microscopic pen could draw structures small enough to trap light

Image credit: Dreamstime

A Cambridge-based team of researchers has developed a novel technique for drawing on tiny crystals, using ink droplets deposited with a commercially available printing method.

According to the researchers, this approach could be used to develop new sensors and lasers, and to investigate interactions between light and matter.

The technique was made possible by applying high-resolution inkjet printing to the field of nanophotonics: the field of study concerning light on the scale of individual molecules. Advances in inkjet printing now allow for the efficient printing of very small devices using various substances as ink, including living cells.

“Most inkjet printers push the ink through the nozzle by heating or applying pressure, producing ink droplets about the size of the diameter of a human hair,” said Dr Vincenzo Pecunia, first author of the Advanced Materials study detailing the research.

The team – made up of researchers from the University of Cambridge and the Hitachi Cambridge Laboratory – found that their ultra-high-resolution electrohydrodynamic jet printer (which applies a voltage to ink to push it through a tiny nozzle to achieve 10 to 100 times better resolution than standard printers) could be used to print structures tiny enough to be useful in nanophotonics.

“Previous efforts to combine these two areas had bumped into the limitations of conventional inkjet printing technology, which cannot directly deposit anything small enough to be comparable to the wavelength of light,” said Dr Pecunia. “But through electrodynamic inkjet printing we’ve been able to move beyond these limitations.”

The electrohydrodynamic printer allows for nanoscale droplets of ink to be ‘drawn’ onto photonic crystals as though with an ultra-fine pen. This allowed the researchers to rapidly draw patterns on top of the crystals, adapting their properties such that they could trap light inside them.

Light trapped by a tiny droplet on a photonic crystal surface.

University of Cambridge

Image credit: University of Cambridge

The patterns can be drawn with a range of printable materials, and the photonic crystal can be washed clean and reused after printing.

“This fabrication technique opens the door for diverse opportunities in fundamental and applied sciences,” said Dr Frederic Brossard of the Hitachi Cambridge Laboratory. According to Dr Brossard, this new technique could be used to create high density, high sensitivity sensors to monitor biomolecules such as viruses or cancer cells.

It could also be used to create lasers, study unexplored phenomena requiring strong interaction between light and matter in new materials, and develop compact, adaptable optical circuits which guide light through a crystal template.

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