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

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