  An experimental study of laser pulse duration influence on the terahertz
emission during single-color filamentation is carried out. It is shown that for
each terahertz frequency there is an optimal laser pulse duration providing
maximal generation at constant pulse energy. It is demonstrated that longer
pulses are required for stronger low-frequency terahertz emission, thus despite
considerable laser peak power decreasing the terahertz radiation yield can be
increased by more than 3 times.
