Figure 4. Amplification and suppression of plasma oscillations.
Eprobe (t, τ) traces measured by scanning the electro-optic sampling time τ at selected pump-probe delays t = 0 ps and t = 2 ps. Data are shown along with the same quantity measured at equilibrium (pump off). Plasma oscillations on the trailing edge of the pulses (τ ≳ 2 ps) are highlighted by thicker lines. Colored shadings in a and b indicate amplification and suppression of the JPW amplitude, respectively.