Compact source of continuously and widely-tunable terahertz radiation.

We report a THz radiation source based on the technique of non-collinear phasematched parametric generation. The source, which is compact and operable at room temperature, generates nanosecond pulses of peak power and energy greater than 1W and 5 nJ respectively. The radiation is continuously tunable over the range 1.2-3.05 THz and is of narrow spectral bandwidth (<100 GHz). The use of intersecting pump and parametric wave cavities results in threshold pump pulse energies below 1 mJ (from a Nd:YAG laser excited at 20 W, 500 microsec by a quasi-CW diode-laser) and close to 50% down-conversion efficiency when operated at twice threshold.