  We show that coherently driven atomic or molecular media potentially yield
strong controllable short pulses of THz radiation. The method is based on
excitation of maximal quantum coherence in a gas medium by optical pulses and
coherent scattering of infra-red radiation to produce pulses of THz radiation.
The pulses have the energies range from several nJ to $\mu$J and time durations
from several fs to ns at room temperature.
