Generation of monochromatic nanosecond pulses in the FIR region

We present a technique for generating short far-infrared (FIR) laser pulses , with a linewidth close to the Fourier transform limit, changing the refle ctivity of an InSb crystal by the photoelectric effect. The crystal is irra diated with an optically pumped CW FIR laser and its reflectivity at an FIR frequency is changed by the ionizing radiation of a pulsed Nd-YAG laser. A reflectivity change, from 18 to 90%, has been obtained. Shorter FIR pulses can be obtained using shorter ionizing laser pulses. Finally, double pulse s separated by an arbitrary time interval and of chosen amplitude are obtai ned.