Electrooptic sampling of freely propagating terahertz fields

The electrooptic measurement of freely-propagating, subpicosecond pulsed electromagnetic waves (terahertz fields) are presented. A LiTaO₃ crystal was used as a sensor head and achieved subpicosecond temporal resolution and 22 mVcm^–1Hz^–1/2 field sensitivity. The flat frequency response from the electrooptic crystals permitted the detection of radiation with ultrawide bandwidth and overcame previous limitations imposed by the resonant structure of photoconductive dipole antennas.