We describe a technique to extract electro-optic Cherenkov radiation from a LiTaO3 crystal into free space. This permits the generation of collimated beams of terahertz radiation into free space and overcomes previous limitations imposed by total internal reflection.

When illuminated by ultrashort optical pulses, large aperture planar photoconductors are shown to radiate a directional electromagnetic pulse which can be steered by varying the angle of incidence of the optical beam.