Terahertz radiation from ultrahigh-speed field-effect transistors induced by ultrafast optical gate switching

We have observed terahertz radiation due to ultrafast change in drain current induced by optical gate-field modulation in high-speed field-effect transistors (FETs). This time-domain measurement is potentially applicable to the characterization of cutoff frequencies of ultrahigh-speed FETs beyond the frequency range covered by conventional swept-frequency measurements. The cutoff frequencies of sample FETs deduced by the present technique were in good agreement with those determined by a network analyzer.