Optimum excitation conditions for the generation of high-electric-field terahertz radiation from an oscillator-driven photoconductive device

We report the impulsive generation of terahertz (THz) radiation with a field amplitude of more than 1.5 kV/cm at megahertz repetition rates, using an interdigitated photoconducting device. The approach provides an average THz power of 190 microW, corresponding to an optical-to-THz conversion efficiency of 2.5 x 10(-4). Optimum conditions are achieved when the excitation spot size is of the order of the THz wavelength.