A nanoscopic light house to shine on proteins

More accurate medical diagnostics and much faster telecommunication. Those are the promises of a ‘nanoscopic light house’ recently invented by optics researcher Prof. Taco Visser and colleagues.

Making light behave out of the ordinary. That is what Prof. Taco Visser answers when asked what his work is about. The researcher made light chase its own tail, created optical tornado’s and fidgeting with surface plasmons (the intricate interplays between photons and electrons). Now Visser, who works at the EEMCS faculty and the Free University of Amsterdam, can add yet another feat to his list of optics eccentricities; a nanoscopic torch or, how he prefers to say, a nanoscopic light house.

Visser and colleagues from Delft and Amsterdam and from the Institut d’Optique in Paris were able to steer the direction of light emanating from a tiny (sub wavelength) slit carved out of a thin golden film. They did so by adjusting the phase of the light entering the opening. Their findings were published last month in Physical Review Letters.

If miniaturized this technique could result in a nanoemitter with which one can steer light in any desired direction without the use of any mechanical or optical elements. “And that is of importance for many applications in medical diagnostics and telecommunication”, says Visser.

“Light can for instance be used to trigger chemical reactions causing certain proteins in biological samples to fluoresce so you can detect them. For that you want to be able to steer the light very precisely. And in telecommunication a switch that can send light coming out of a nano-aperture left or right into different glass fibres doesn’t exist yet and could be of great use.”

In order to adjust the phase of the light entering the nanoslit (and thus in turn steer the light emanating from it) the researchers now combine three large laser beams. “With this apparatus we proved the physical feasibility ”, says Visser. “We are now going to miniaturize the emitter by letting a hologram change the phase of laser light.”

S.B. Raghunathan et. Al., Dynamic beam steering from a subwavelength slit by selective excitation of guided modes, Physical review letters, 11 October 2013



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