NTT: Petahertz Frequency Observed in Gallium Nitride

Researchers at NTT and Tokyo University of Science  observed electronic oscillation (dipole oscillation) with attosecond (as: 10-18 of a second) periodicity using gallium nitride (GaN) wide-bandgap semiconductor. The experiment marks the first time the petahertz frequency barrier has been exceeded with a semiconductor. NTT said this shows the potential of future petahertz signal processing technology based on ordinary wide-bandgap semiconductor devices.

Previously, the maximum operational frequency was in the terahertz (1012 Hz) range, which was limited by the response time of band energy modulation with RF electric fields. To observe the ultrafast electron motion with petahertz frequency, extremely high temporal resolution was required.

http://www.ntt.co.jp/news2016/1604e/160411b.html