"With pure silicon," says Biaggio, "you can build waveguides that enable you to control light beam propagation, but you cannot get ultrafast light-to-light interaction. Using only silicon, people have achieved a data switching rate of only 20 to 30 gigabits per second, and this is very slow.
"We need higher-speed switching to achieve a higher bit rate. Organic materials can do this, but they are not terribly good for building waveguides that control propagation of tightly confined light beams."
To combine the strengths of the DDMEBT and the silicon, Biaggio and his collaborators have fashioned silicon-organic hybrid (SOH) waveguides where silicon waveguides are covered with DDMEBT.
"We have combined the two approaches," he says. "We start from a silicon waveguide designed to guide the light between two silicon ridges . Then we use molecular beam deposition to fill the space between the ridges with the organic material [DDMEBT], creating a dense plastic with high optical quality and high nonlinearity where the light propagates.
"We combine the best of both technologies."
One of the group's singular achievements, he says, is the filling-in process.
"The key question was whether we could put the DDMEBT between the two silicon strips. There is a lot of research in this area, but no one had been able to make an organic material completely and homogeneously cover such a silicon structure, so that it spreads out and fills all the spaces. Homogeneity is necessary to prevent light scattering and losses.
We now achieved this by using a molecular structure that decreases inter-molecular interactions and promotes the formation of a homogeneous solid state. We then heated the molecules to a vapor phase and used a molecular beam to deposit the molecules on top of the silicon structure. The molecules were able to homogeneously fill the nanometer scale slot between the silic
|Contact: Kurt Pfitzer|