The result is a laser that emits picosecond pulses of light at a frequency of 40 gigahertz. “This thing puts out short pulses of light, which is what you need for high-speed communication,” says Bowers. “If you pulse at 40 gigahertz and combine that with a modulator [which puts information onto the light], then you have a light source.”
The work “represents some nice progress toward proving a laser source on a silicon wafer,” says Ivan Kaminow, professor of electrical engineering and computer science at the University of California, Berkeley, but he cautions that silicon photonics still has a long way to go. “Silicon is not an optimum photonic material,” he says. “The hybrid approach is a compromise and, as such, is far from optimum performance.” For instance, the hybrid laser can’t operate at the same high temperatures that silicon circuits do.
Bowers agrees that there is still work to be done, and improving the device’s temperature threshold is on the list. “This is pretty far-out research,” he says. “Our goal last year was just to make a good laser on silicon, and now we’re expanding that not just to do lasers, but photonic integrated-circuit technology.” He suspects that silicon photonic devices based on his group’s approach could appear in products as early as 2012.