A team of scientists report a communications breakthrough that they say could be used to speed up electronic devices by a factor of one thousand.
The University of Pittsburgh team claims to have successfully generated a frequency comb, which entails dividing a single color of light into a series of evenly spaced spectral lines for a variety of uses, that spans more than 100 terahertz (THz, or 1 trillion cycles per second) bandwidth.
Terahertz radiation is the portion of the electromagnetic spectrum between infrared and microwave light.
Hrvoje Petek, a professor of physics and chemistry at Pitt, said that this has been long-awaited discovery in the field. Petek and his team generated the all-optical frequency comb by investigating the optical properties of a silicon crystal and "exciting a coherent collective of atomic motions in a semiconductor silicon crystal" with an intense laser pulse.
First, they observed that the amount of reflected light oscillates at 15.6 THz, the highest mechanical frequency of atoms within a silicon lattice. The oscillation then caused additional changes in the absorption and reflection of light, multiplying the fundamental oscillation frequency by up to seven times, which then generated the comb of frequencies extending beyond 100 THz.
"Although we expected to see the oscillation at 15.6 THz, we did not realize that its excitation could change the properties of silicon in such dramatic fashion," says Petek. "The discovery was both the result of developing unique instrumentation and incisive analysis by the team members."
According to a news release, the team is now investigating the coherent oscillation of electrons, which could further extend the ability of harnessing light-matter interactions from the terahertz- to the petahertz-frequency range. Petahertz frequencies scale up to 1 quadrillion hertz.
The research is published in Nature Photonics and is funded by the National Science Foundation.