$6 Million Project To Develop Silicon-based Laser
The Microphotonics Center at the Massachusetts Institute of Technology (MIT) has begun a $3.6 million research project into silicon-based lasers and nanophotonics.
Funded by the US Government s Department of Defense (DoD) under the multi-university research initiative (MURI) program, the project, titled Electrically Pumped Silicon Based Lasers for Chip-Scale Nanophotonic Systems, is led by Lionel Kimerling, director of MIT s Materials Processing Center and Microphotonics Center.
Although optically-pumped silicon lasers have been produced by Intel among others, electrical pumping has so far proved elusive - largely because of silicon s indirect bandgap. But if silicon can be made to lase in this way, it could have a major effect on III-V optoelectronics.
The MURI project includes collaborators from eight US universities, as well as teams in Toronto and McMasters in Canada, Catania and Trento in Italy and FOM in the Netherlands.
Jürgen Michel, principal investigator at MIT s Microphotonics Center, explained how the technology could be used in on-chip communications:
"You could connect the cores in your chip optically, increasing speed and efficiency. By the same technique you could connect to the memory section of the chip. The effect would be faster on-chip communications and lower power demands.
"You could also use the silicon-based laser to connect the chip to other devices outside. Such a laser would open a whole new area of chip design. Optical devices, including lasers could be processed together with transistors on the same chip, using the same toolset."
The research partners are considering two approaches. The first aims to use nanocrystalline silicon in combination with erbium to produce a 1550 nm source. This will be based in a dielectric matrix such as SiO2 or Si3N4.
Such an environment can be an efficient sensitizer for erbium, Michel explains. "We trap electron-hole pairs in the nanocrystal. Upon recombination, the energy will be efficiently transferred to an erbium ion that then will emit light at 1550 nm. A key is to use optical resonators to enhance the light emission. The big question is whether we can achieve successful resonator emission at room temperature."
The second approach is to use a germanium layer deposited on silicon as the active laser material. In this case, the germanium is modified to act as a direct bandgap semiconductor, which could create a high-power light source in the milliwatt range. "An advantage with this approach is that we could integrate the device into a fiber-optic network," he added.
"Either way, these devices will be integrated into a CMOS process. We want to integrate these optical devices on a microchip; we want to be able to make millions of them."