Generation of narrowband terahertz radiation by an ultrashort laser pulse in a bulk LiNbO 3 crystal

We show that a femtosecond laser pulse propagating in a LiNbO3 crystal as a superposition of ordinary and extraordinary waves can efficiently generate narrowband terahertz radiation in a quasi-phase-matched regime. The generation mechanism is similar to that in periodically poled crystals, although it occurs in a bulk crystal. In particular, a 600 fs pulse from a Yb-doped laser amplifier can generate radiation at ∼0.5  THz with bandwidth of 3.6 GHz and efficiency ∼10−5. Frequency tuning can be achieved by tilting the laser beam in the crystal. The predicted effect can be used for creating tunable spectrally bright terahertz sources.