Subpicosecond Nonlinear Plasmonic Response Probed by Femtosecond Optical Pulses

The hydrodynamic model of the electron transport in the channel of a nanoscale field effect transistors predicts that three different electron transport regimes – collision-dominated, ballistic, and viscosity dominated – determine the ultimate response time of the semiconductor device depending on its length, momentum relaxation time, and viscosity. The characteristic response times of ultra-short channel transistors are in the subpicosecond range. We now report on a new measurement technique with a greatly enhanced sensitivity using optical band-to-band pulses with a controlled delay. The measurements using this new electro-optic sampling and hydrodynamic modeling reveal the ultra-fast transistor plasmonic response at the time scale much shorter than the electron transit time.