Fig. 3. Terahertz radiation by the resonant excitation of even- and odd-parity excitons with ω- and 2ω-pulses in [Ni(chxn)₂Br]Br₂.

Schematic diagram of the ω- and 2ω-pulse injection with the delay time (a) $\mathrm{\Delta }t~0$ fs and (c) $\mathrm{\Delta }t~60$ fs on to a crystal. Electric-field waveforms of terahertz radiations at (b) $\mathrm{\Delta }t~0$ fs and (d) $\mathrm{\Delta }t~60$ fs.