European researchers has demonstrated some of the first commercially viable plasmonic devices, paving the way for a new era of high-speed communications and computing in which electronic and optical signals can be handled simultaneously. The Plasmocom technology can create plasmonic devices using existing commercial lithography techniques.
Zayats notes that interest in the team’s work has been extensive within both academia and industry, evidenced by the success of a workshop in June in Amsterdam attended by representatives of several photonics and electronics firms, including NEC and Panasonic.
“I think that we will start to see this technology make its way into commercial applications over the next five to ten years,” Zayats says. “A key breakthrough will be using plasmonics for inter-chip communication, making it possible to transmit data between one or more chips at optical speeds and eliminating a major bottleneck to faster computers.”
The pioneering devices, which are expected to lead to commercial applications within the next decade, make use of electron plasma oscillation to transmit optical and electronic signals along the same metal circuitry via waves of surface plasmon polaritons. In contrast, signals in electronic circuits are transmitted by electrons, while photons are used to carry data in optical systems.
Up until this work an all optical computer would be too big (minimumum size for the last five years would be big as an oven) and plasmonic communication only worked over short distances.
Current commercial optical ring resonators have a radius of up to 300 micrometres, the plasmonic demonstrator built by the Plasmocom team measured just five micrometres. The new devices have dimension 60 times less.
Plasmonic data transmission functions on the basis of oscillations in the electron density at the boundary of two materials: a dielectic (non-conductive) plasma or polymer and a metal surface. By exciting the electrons with light it is possible to propagate high-frequency waves of plasmons along a metal wire or waveguide, thus transmitting a data signal. However, in many cases the signal dissipates after only a few micrometres – far too short to interconnect two computer chips, for example.
The Plasmocom team took a novel approach, developing what they called dielectric-loaded surface plasmon polariton waveguides (DLSPPW). By patterning a layer of various polymer (polymethyl methacrylate) dielectic onto gold film supported by a glass substrate, they were able to achieve waveguides that were only 500 nanometres in size while extending the signal propagation.
Using this approach, the researchers built a variety of plasmonic devices, including low-loss S bends, Y-splitters and a waveguide ring resonator, a crucial part of the add-drop multiplexers (ADM) in optical networks that combine and separate several streams of data into a single signal and vice versa.