Abstract

We show that a femtosecond laser pulse propagating in a ${\mathrm{LiNbO}}_3$ 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 $\sim 0.5\mathrm{THz}$ with bandwidth of 3.6 GHz and efficiency $\sim {10}^{-5}$. 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.

© 2017 Optical Society of America

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