Fig. 2. (a) THz time-domain waveforms and (b) THz frequency-domain spectra with different modulation powers. The pump power is set as 0.6 W.
Fig. 3. (a) THz signal of three representative excitation pump powers of 0.4 W, 0.6 W, and 0.8 W in the presence of pre-formed plasma as a function of the relative time between the pump beam and the modulation beam. (b) The effect of the modulated laser intensity on the THz wave modulation depth.