Radiation patterns from lens-coupled terahertz antennas.

We report on investigations of the angular distribution of the radiation emitted from a terahertz antenna system equipped with a truncated spherical silicon lens. The pattern is calculated by wide-angle interference principles and Huygens-Fresnel diffraction theory. Experimental determination of the radiation pattern is performed by spatially resolved terahertz time-domain spectroscopy. Good agreement between theory and experiment is obtained, and we find that the terahertz beam can be represented by a Gaussian beam emitted from a circular aperture equal to the diameter of the lens.