NANOPHOTONICS: Europe invests in plasmonics

A European consortium lead by the Swiss Centre for Electronics and Microtechnology (CSEM; Neuchatel) has initiated a €2.8 million (US$3.6 million) project in plasmonics.

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A European consortium lead by the Swiss Centre for Electronics and Microtechnology (CSEM; Neuchatel) has initiated a €2.8 million (US$3.6 million) project in plasmonics. The project, called PLEAS (Plasmon Enhanced Photonics), aims to bring plasmonics out of the lab and into the European photonics industry. The investment comes through the Sixth Framework Programme, a transnational research promotion and funding organization coordinated by the European Union (EU).

The PLEAS consortium headed by CSEM also includes light-emitting-diode (LED) maker Osram Opto Semiconductor (Regensburg, Germany) and Sagem Défense Sécurité (Paris, France), a key player in vision-based security technology. The project’s academic partners include the Autonomous University of Madrid, the University of Zaragoza, Queens University Belfast, the Technical University of Dresden, and the Louis Pasteur University (Strasburg, Germany).

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An optical field is enhanced by plasmonic interactions near a gold particle. Orange regions are areas of high intensity. The penetration of the optical field into the particle is evident. (Courtesy of CSEM)
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Plasmonics involves the manipulation of surface plasmons (SPs; electron waves that propagate along the surface of a conductor). By altering the structure of a metal surface, the interaction of plasmons with light can be modified, offering the potential for revolutionizing photonic systems. Surface plasmons can help overcome the diffraction limits of size and performance in photonic components. For example, plasmon effects can allow subwavelength arrays of holes in a metal film to transmit light and act as spectral filters. At certain wavelengths the transmission is enhanced and can be several times the combined area of the holes.

“On one hand, the European research community is the world leader in almost every area of plasmon research; on the other hand, the huge potential of plasmons had not been supported adequately by the photonics industry,” says Ross Stanley, project coordinator of PLEAS. “In this project, we have the top plasmon experts sitting around the same table as two major players from the European photonics industry, explaining their vision of how plasmonics can revolutionize photonics.”

Surface plasmons are being explored for their potential in photolithography, data storage, spectroscopy, microscopy, and biophotonics. The PLEAS project has two main applications in mind, according to the industrial partners. Osram Opto Semiconductor is interested in plasmonics as a way of achieving higher-efficiency LEDs. Surface plasmons can help the efficiency of light-emitting devices because the metal electrodes of such devices, which are normally a source of loss, can instead by used to enhance light extraction. Suitable metals such as gold, silver, or aluminum structured with arrays of holes will be used in this way. “We aim to improve these devices’ efficiencies by at least 20%, in either overall efficiency or in directionality, so that a premium LED that is already typically 35% efficient could be improved to have an efficiency nearer 50%,” says Stanley.

In a second research focus, Sagem Défense Sécurité aims to develop higher-sensitivity photodetectors that will lead to cheaper and more powerful cameras.

The team aims to improve the signal-to-noise ratio of these devices by using a small detector positioned behind a tiny hole in a metal plate. “By using a 50 × 50 nm detector behind a nanostructured 5 × 5 µm gold plate, one can dramatically reduce the noise, while maintaining detector efficiency and sensitivity,” Stanley notes.

Bridget Marx

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