Terahertz radiation from a photoconducting antenna array

An array of photoconducting antennas which generates electrically controllable millimeter-wave and submillimeter-wave radiation in free space is described. Under quasi-sinusoidal optical illumination, the emitted radiation is directional and electrically steerable, and can be scanned through an angle of over 40°. The center of the scanning range can be adjusted by changing the angle of incidence of the pump beam. The far-field radiation pattern of the array is measured and discussed. Also, some properties of the array under illumination by a short optical pulse are demonstrated. These include electrical control of the frequency content of the signal and mapping of the spatial profile of the applied electric field onto the radiated waveform. The latter property can be used to multiplex information presented in parallel into a train of radiated pulses with a bit spacing of 6 ps