Researchers at MIT and Israel’s Technion developed a method to accelerate the momentum of photons to match the momentum of electrons. This process allows both particles to interact strongly with the possible outcome of developing new types of lasers, color-tunable LEDs, silicon photonics and more efficient solar cells.
Normally the momentum of photons is several orders of magnitude larger than that of electrons, causing the interaction between both to be very weak. However, if it is possible to bring both momenta closer to each other, the interaction between light and matter can be strong and controllable.
A combination of a layer of graphene with GaAs and InGaAs increases light-matter interaction. Source: MIT
The researchers, led by Yaniv Kurman of the Israel Institute of Technology in Haifa (Technion for short) were trying to match the momenta of both photons and semiconductor materials such as silicon, or the composite materials, in order to improve the interaction of light with these materials. Applications that involve light such as solar cells or LEDs is a case in point. Despite the fact that it is very inefficient in converting light into electricity, silicon is the basis of many semiconductor devices.
“Most people looking into this problem have focused on the silicon itself, but this approach is very different — we’re trying to change the light instead of changing the silicon,” Technion's Ido Kaminer said. "People design the matter in light-matter interactions, but they don’t think about designing the light side.”
To make the interaction more efficient, the researchers developed a theoretical approach and showed that by slowing down the momentum of photons to the point where both – electrons and photons - momenta are similar, light can be absorbed and emitted by the semiconductor. It is possible, they found, to slow light by a factor of 1,000 by filtering it through a multilayered thin-film material made of gallium arsenide and indium gallium arsenide with a layer of graphene on the surface of the structure, as is shown in the image above.
The result of this preliminary experiment was published in the journal Nature Photonics last week.
“The work is very general,” according to Kurman, so the results should apply to many more cases than the specific ones used in this study. “We could use several other semiconductor materials, and some other light-matter polaritons.”
While this work was not done with silicon, it should be possible to apply the same principles to silicon-based devices, the team says.
“By closing the momentum gap, we could introduce silicon into this world (of plasmon-based devices)," Kurman said.
