Generation, tuning, and shaping of narrow-band, picosecond THz pulses by two-beam excitation.

We demonstrate the use of a transient polarization grating induced by two femtosecond laser pulses propagating in a LiNbO3 crystal for the generation of frequency tunable, narrow-band, picosecond THz pulses. Employing pump pulses with 150 fs duration and 2 J energy, the generated THz pulse has an energy up to 1.8 pJ, a pulse duration of 3 - 5 ps and a bandwidth of 0.