HIGH-INTENSITY TERAHERTZ PULSES AT 1-KHZ REPETITION RATE

We report the generation of terahertz pulses with 0.4-mu J pulse energ y at 1-kHz repetition rate using a large-aperture GaAs photoconductor with 3-cm gap aluminum electrodes, biased at voltages up to 45 kV, The terahertz output energy saturates at a laser fluence of 40 mu J/cm(2) at low-bias fields, while no clear saturation point was observed at h igh-bias fields, The output was found to be dependent on the repetitio n rate: at high fluences, pulse energy at 1 kHz is higher than that at 100 Hz by as much as 60%. A study of the behavior of the terahertz pu lse energy and pulsewidth as a function of the pulsewidth of the laser excitation was conducted and compared with theoretical predictions. P ropagation properties of the terahertz beam were also characterized, l eading to a focal spot size as small as 800 mu m at the focus of a 2.5 -in focal length parabolic mirror.