For more than 50 years researchers have been exploring the potential of surface plasmons, the tiny waves of electrons that form when light illuminates a metal surface. Now Dr. Muhammad Alam is looking to advance our understanding of, and find new uses for, this rapidly growing, leading-edge technology.
“Light creates ripples in the sea of electrons in metal—very much like the waves created by a stone thrown in water,” says Dr. Alam. “These tiny waves, surface plasmons (SP), can be used to trap light so that instead of being reflected back from the metal, light becomes very highly confined on the metal surface. Since SP is trapped on the metal surface, it is very sensitive to any change happening near the metal surface. For example, if a biomolecule is trapped on the surface, it will significantly affect the SP and this can be used to detect the presence of the molecule.”
While offering a vast array of potential applications, the promise of plasmonics is hindered by a major limitation: rapid loss of energy as the light trapped on the SP propagates. Dr. Alam’s work is addressing this challenge. “The power carried by light quickly dissipates in the form of heat in the metal,” he explains.
A graduate of University of Toronto’s Department of Electrical & Computer Engineering, Dr. Alam’s award-winning investigations into plasmonics stem from his PhD thesis. Under the co-supervision of Professors Stewart Aitchison and Mo Mojahedi, he proposed a hybrid plasmonic waveguide (HPWG) structure that would maintain the strong light confinement ability of surface plasmons while greatly reducing the loss of energy.
His hybrid plasmonic waveguide is constructed by separating a silicon film from a metal surface by introducing a small gap. The HPWG concentrates power in the region between the metal and the film. “This approach provides a good compromise between propagation loss and light confinement ability,” he says.
A key feature of his HPWG is that its fabrication is compatible with silicon technology. This means that both the HPWG and a silicon waveguide can be integrated on the same chip, allowing the researcher to take advantage of the distinctive properties and performance of two promising technologies—silicon photonics and plasmonics—all on the same chip.
The HPWG could lead to the development of many new types of devices that use plasmonics, which could contribute to advancements in bio-sensing, optical interconnect, compact optical devices, and optical switch research. There are many such applications in engineering and health sciences, and can build on the SP capability, which is already being used to detect chemical compounds.
Alam’s transformative development of the hybrid plasmonic waveguide system has generated considerable attention. His thesis has resulted in 13 publications in high-impact journals, 20 conference publications, and eight invited talks. His research contributions have been cited over 270 times, with 107 citations in 2013 alone. The research has already provided core enabling technology for the development of various commercial products, including high-performance optical switches, smaller and faster communication chips, and highly sensitive optical biosensors for disease diagnosis.
A rising star in the field of plasmonics, the University of Toronto post-doctoral fellow is the 2013 winner of CMC Microsystems’ Douglas R. Colton Medal for Research Excellence. Alam says he is thrilled to win the award, which recognizes excellence in research leading to new understanding and novel developments in microsystems and related technologies.